2024-03-29T05:13:07Zhttp://oai.recercat.cat/request
oai:recercat.cat:2072/2636862017-05-23T04:24:33Zhdl_2072_169514Rapid and multiband variability of the TeV bright active nucleus of the galaxy IC 310MAGIC CollaborationMarcote Martin, BenitoMoldón Vara, Francisco JavierMunar i Adrover, PereParedes i Poy, Josep MariaRibó Gomis, MarcZanin, RobertaGalàxies activesAstronomia de raigs XAstronomia de raigs gammaRaigs còsmicsAstrofísicaActive galaxiesX-ray astronomyGamma ray astronomyCosmic raysAstrophysicsThe radio galaxy IC 310 has recently been identified as a γ-ray emitter based on observations at GeV energies with Fermi-LAT and at very high energies (VHE, E > 100 GeV) with the MAGIC telescopes. Originally classified as a head-tail radio galaxy, the nature of this object is subject of controversy since its nucleus shows blazar-like behavior. Aims. To understand the nature of IC 310 and the origin of the VHE emission, we studied the spectral and flux variability of IC 310 from the X-ray band to the VHE γ-ray regime. Methods. The light curve of IC 310 above 300 GeV has been measured with the MAGIC telescopes from 2009 October to 2010 February. Contemporaneous Fermi-LAT data (2008−2011) in the 10−500 GeV energy range were also analyzed. In the X-ray regime, archival observations from 2003 to 2007 with XMM-Newton, Chandra, and Swift-XRT in the 0.5−10 keV band were studied. Results. The VHE light curve reveals several high-amplitude and short-duration flares. Day-to-day flux variability is clearly present (>5σ). The photon index between 120 GeV and 8 TeV remains at the value Γ ~ 2.0 during both low and high flux states. The VHE spectral shape does not show significant variability, whereas the flux at 1 TeV changes by a factor of ~7. Fermi-LAT detected only eight γ-ray events in the energy range 10 GeV<br>500 GeV in three years of observation. The measured photon index of Γ = 1.3 ± 0.5 in the Fermi-LAT range is very hard. The X-ray measurements show strong variability in both flux and photon index. The latter varied from 1.76 ± 0.07 to 2.55 ± 0.07. Conclusions. The rapid variability measured in γ-rays and X-rays confirms the blazar-like behavior of IC 310. The multi-TeV γ-ray emission seems to originate from scales of less than 80 Schwarzschild radii (for a black hole mass of 2 × 108 M⊙) within the compact core of its FR I radio jet with orientation angle 10°−38°. The spectral energy distribution resembles that of an extreme blazar, albeit the luminosity is more than two orders of magnitude lower.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/58575eng(c) Springer Verlag, 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2636892017-05-23T04:24:37Zhdl_2072_169514Discovery of very high energy gamma-ray emission from the blazar 1ES 1727+502 with the MAGIC TelescopesMAGIC CollaborationMarcote Martin, BenitoMoldón Vara, Francisco JavierMunar i Adrover, PereParedes i Poy, Josep MariaRibó Gomis, MarcZanin, RobertaGalàxiesRaigs gammaTelescopisNucli galàctic actiuAstrofísicaGalaxiesGamma raysTelescopesActive galactic nucleiAstrophysicsMotivated by the prediction of a high TeV luminosity we investigated whether the blazar 1ES 1727+502 (z = 0.055) is emitting very high energy (VHE, E > 100 GeV) γ rays. We observed the BL Lac object 1ES 1727+502 in stereoscopic mode with the two MAGIC telescopes for 14 nights between May 6th and June 10th 2011, for a total effective observing time of 12.6 h. To study the multiwavelength spectral energy distribution (SED), we used simultaneous optical R-band data from the KVA telescope, archival UV/optical and X-ray observations from instruments UVOT and XRT on board of the Swift satellite, and high energy (HE, 0.1 GeV-100 GeV) γ-ray data from the Fermi-LAT instrument. We detected, for the first time, VHE γ-ray emission from 1ES 1727+502 at a statistical significance of 5.5σ. The integral flux above 150 GeV is estimated to be (2.1 ± 0.4)% of the Crab nebula flux and the de-absorbed VHE spectrum has a photon index of (2.7 ± 0.5). No significant short-term variability was found in any of the wavebands presented here. We model the SED using a one-zone synchrotron self-Compton model obtaining parameters typical for this class of sources.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/58584eng(c) Springer Verlag, 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2636922017-05-23T04:24:40Zhdl_2072_169514Contemporaneous observations of the radio galaxy NGC 1275 from radio to very high energy γ-raysMarcote Martin, BenitoMunar i Adrover, PereParedes i Poy, Josep MariaParedes Fortuny, XavierPersic, M.Ribó Gomis, MarcZanin, RobertaMAGIC CollaborationGalàxiesGalàxies activesJets (Astrofísica)Raigs gammaAstrofísicaGalaxiesActive galaxiesAstrophysical jetsGamma raysAstrophysicsThe radio galaxy NGC 1275, recently identified as a very high energy (VHE, >100 GeV) γ-ray emitter by MAGIC, is one of the few non-blazar active galactic nuclei detected in the VHE regime. The purpose of this work is to better understand the origin of the γ-ray emission and locate it within the galaxy. Methods: We studied contemporaneous multifrequency observations of NGC 1275 and modeled the overall spectral energy distribution. We analyzed unpublished MAGIC observations carried out between October 2009 and February 2010, and the previously published observations taken between August 2010 and February 2011. We studied the multiband variability and correlations by analyzing data of Fermi-LAT in the 100 MeV-100 GeV energy band, as well as Chandra (X-ray), KVA (optical), and MOJAVE (radio) data taken during the same period. Results: Using customized Monte Carlo simulations corresponding to early MAGIC stereoscopic data, we detect NGC 1275 also in the earlier MAGIC campaign. The flux level and energy spectra are similar to the results of the second campaign. The monthly light curve above 100 GeV shows a hint of variability at the 3.6σ level. In the Fermi-LAT band, both flux and spectral shape variabilities are reported. The optical light curve is also variable and shows a clear correlation with the γ-ray flux above 100 MeV. In radio, three compact components are resolved in the innermost part of the jet. One of these components shows a similar trend as the Fermi-LAT and KVA light curves. The γ-ray spectra measured simultaneously with MAGIC and Fermi-LAT from 100 MeV to 650 GeV can be well fitted either by a log-parabola or by a power-law with a subexponential cutoff for the two observation campaigns. A single-zone synchrotron-self-Compton model, with an electron spectrum following a power-law with an exponential cutoff, can explain the broadband spectral energy distribution and the multifrequency behavior of the source. However, this model suggests an untypical low bulk-Lorentz factor or a velocity alignment closer to the line of sight than the parsec-scale radio jet.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/58589eng(c) Springer Verlag, 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2636932017-05-23T04:24:56Zhdl_2072_169514Measurement of the Crab Nebula spectrum over three decades in energy with the MAGIC telescopesMAGIC CollaborationMarcote Martin, BenitoMunar i Adrover, PereParedes i Poy, Josep MariaParedes Fortuny, XavierRibó Gomis, MarcZanin, RobertaRaigs gammaPúlsarsTelescopisAstrofísicaGamma raysPulsarsTelescopesAstrophysicsThe MAGIC stereoscopic system collected 69 hours of Crab Nebula data between October 2009 and April 2011. Analysis of this data sample using the latest improvements in the MAGIC stereoscopic software provided an unprecedented precision of spectral and night-by-night light curve determination at gamma rays. We derived a differential spectrum with a single instrument from 50 GeV up to almost 30 TeV with 5 bins per energy decade. At low energies, MAGIC results, combined with Fermi-LAT data, show a flat and broad Inverse Compton peak. The overall fit to the data between 1 GeV and 30 TeV is not well described by a log-parabola function. We find that a modified log-parabola function with an exponent of 2.5 instead of 2 provides a good description of the data (χred2 = 35 / 26). Using systematic uncertainties of the MAGIC and Fermi-LAT measurements we determine the position of the Inverse Compton peak to be at (53 ±3stat +31syst -13syst) GeV, which is the most precise estimation up to date and is dominated by the systematic effects. There is no hint of the integral flux variability on daily scales at energies above 300 GeV when systematic uncertainties are included in the flux measurement. We consider three state-of-the-art theoretical models to describe the overall spectral energy distribution of the Crab Nebula. The constant B-field model cannot satisfactorily reproduce the VHE spectral measurements presented in this work, having particular difficulty reproducing the broadness of the observed IC peak. Most probably this implies that the assumption of the homogeneity of the magnetic field inside the nebula is incorrect. On the other hand, the time-dependent 1D spectral model provides a good fit of the new VHE results when considering a 80 μG magnetic field. However, it fails to match the data when including the morphology of the nebula at lower wavelengths.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/69484engcc-by-nc-nd (c) Elsevier B.V., 2015info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by-nc-nd/3.0/es">http://creativecommons.org/licenses/by-nc-nd/3.0/es</a>
oai:recercat.cat:2072/2636792017-05-23T04:24:57Zhdl_2072_169514The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab NebulaMAGIC CollaborationMarcote Martin, BenitoMunar i Adrover, PereParedes i Poy, Josep MariaParedes Fortuny, XavierRibó Gomis, MarcZanin, RobertaRaigs gammaPúlsarsTelescopisAstrofísicaGamma raysPulsarsTelescopesAstrophysicsMAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in the Canary island of La Palma, Spain. During summer 2011 and 2012 it underwent a series of upgrades, involving the exchange of the MAGIC-I camera and its trigger system, as well as the upgrade of the readout system of both telescopes. We use observations of the Crab Nebula taken at low and medium zenith angles to assess the key performance parameters of the MAGIC stereo system. For low zenith angle observations, the standard trigger threshold of the MAGIC telescopes is ∼ 50 GeV. The integral sensitivity for point-like sources with Crab Nebula-like spectrum above 220 GeV is (0.66 ± 0.03)% of Crab Nebula flux in 50 h of observations. The angular resolution, defined as the σ of a 2-dimensional Gaussian distribution, at those energies is ≲ 0.07°, while the energy resolution is 16%. We also re-evaluate the effect of the systematic uncertainty on the data taken with the MAGIC telescopes after the upgrade. We estimate that the systematic uncertainties can be divided in the following components: < 15% in energy scale, 11%-18% in flux normalization and ± 0.15 for the energy spectrum power-law slope.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/69529eng(c) Elsevier B.V., 2015info:eu-repo/semantics/embargoedAccess
oai:recercat.cat:2072/2636802017-05-23T04:24:59Zhdl_2072_169514The major upgrade of the MAGIC telescopes, Part I: The hardware improvements and the commissioning of the systemMAGIC CollaborationMarcote Martin, BenitoMunar i Adrover, PereParedes i Poy, Josep MariaParedes Fortuny, XavierRibó Gomis, MarcZanin, RobertaRaigs gammaAstrofísicaTelescopisGamma raysAstrophysicsTelescopesThe MAGIC telescopes are two Imaging Atmospheric Cherenkov Telescopes (IACTs) located on the Canary island of La Palma. The telescopes are designed to measure Cherenkov light from air showers initiated by gamma rays in the energy regime from around 50 GeV to more than 50 TeV. The two telescopes were built in 2004 and 2009, respectively, with different cameras, triggers and readout systems. In the years 2011-2012 the MAGIC collaboration undertook a major upgrade to make the stereoscopic system uniform, improving its overall performance and easing its maintenance. In particular, the camera, the receivers and the trigger of the first telescope were replaced and the readout of the two telescopes was upgraded. This paper (Part I) describes the details of the upgrade as well as the basic performance parameters of MAGIC such as raw data treatment, linearity in the electronic chain and sources of noise. In Part II, we describe the physics performance of the upgraded system.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/69530eng(c) Elsevier B.V., 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2636832017-05-23T04:25:02Zhdl_2072_169514Multiwavelength observations of Mrk 501 in 2008MAGIC CollaborationMunar i Adrover, PereParedes i Poy, Josep MariaParedes Fortuny, XavierRibó Gomis, MarcZanin, RobertaRaigs gammaGalàxies activesGalàxiesGamma raysActive galaxiesGalaxiesContext. Blazars are variable sources on various timescales over a broad energy range spanning from radio to very high energy (>100 GeV, hereafter VHE). Mrk 501 is one of the brightest blazars at TeV energies and has been extensively studied since its first VHE detection in 1996. However, most of the γ-ray studies performed on Mrk 501 during the past years relate to flaring activity, when the source detection and characterization with the available γ-ray instrumentation was easier toperform. Aims: Our goal is to characterize the source γ-ray emission in detail, together with the radio-to-X-ray emission, during the non-flaring (low) activity, which is less often studied than the occasional flaring (high) activity. Methods: We organized a multiwavelength (MW) campaign on Mrk 501 between March and May 2008. This multi-instrument effort included the most sensitive VHE γ-ray instruments in the northern hemisphere, namely the imaging atmospheric Cherenkov telescopes MAGIC and VERITAS, as well as Swift, RXTE, the F-GAMMA, GASP-WEBT, and other collaborations and instruments. This provided extensive energy and temporal coverage of Mrk 501 throughout the entire campaign. Results: Mrk 501 was found to be in a low state of activity during the campaign, with a VHE flux in the range of 10%-20% of the Crab nebula flux. Nevertheless, significant flux variations were detected with various instruments, with a trend of increasing variability with energy and a tentative correlation between the X-ray and VHE fluxes. The broadband spectral energy distribution during the two different emission states of the campaign can be adequately described within the homogeneous one-zone synchrotron self-Compton model, with the (slightly) higher state described by an increase in the electron number density. Conclusions: The one-zone SSC model can adequately describe the broadband spectral energy distribution of the source during the two months covered by the MW campaign. This agrees with previous studies of the broadband emission of this source during flaring and non-flaring states. We report for the first time a tentative X-ray-to-VHE correlation during such a low VHE activity. Although marginally significant, this positive correlation between X-ray and VHE, which has been reported many times during flaring activity, suggests that the mechanisms that dominate the X-ray/VHE emission during non-flaring-activity are not substantially different from those that are responsible for the emission during flaring activity. The data for Figs. 2 and 5 are only available at the CDS via anonymous ftp toSpringer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/69565eng(c) Springer Verlag, 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2636842017-05-23T04:25:02Zhdl_2072_169514The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studiesMAGIC CollaborationMunar i Adrover, PereParedes i Poy, Josep MariaParedes Fortuny, XavierRibó Gomis, MarcZanin, RobertaGalàxies activesGalàxiesRaigs gammaNucli galàctic actiuAstrofísicaActive galaxiesGalaxiesGamma raysActive galactic nucleiAstrophysicsAims: We perform an extensive characterization of the broadband emission of Mrk 421, as well as its temporal evolution, during the non-flaring (low) state. The high brightness and nearby location (z = 0.031) of Mrk 421 make it an excellent laboratory to study blazar emission. The goal is to learn about the physical processes responsible for the typical emission of Mrk 421, which might also be extended to other blazars that are located farther away and hence are more difficult to study. Methods: We performed a 4.5-month multi-instrument campaign on Mrk 421 between January 2009 and June 2009, which included VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC, and Whipple, among other instruments and collaborations. This extensive radio to very-high-energy (VHE; E> 100 GeV) γ-ray dataset provides excellent temporal and energy coverage, which allows detailed studies of the evolution of the broadband spectral energy distribution. Results: Mrk421 was found in its typical (non-flaring) activity state, with a VHE flux of about half that of the Crab Nebula, yet the light curves show significant variability at all wavelengths, the highest variability being in the X-rays. We determined the power spectral densities (PSD) at most wavelengths and found that all PSDs can be described by power-laws without a break, and with indices consistent with pink/red-noise behavior. We observed a harder-when-brighter behavior in the X-ray spectra and measured a positive correlation between VHE and X-ray fluxes with zero time lag. Such characteristics have been reported many times during flaring activity, but here they are reported for the first time in the non-flaring state. We also observed an overall anti-correlation between optical/UV and X-rays extending over the duration of the campaign. Conclusions: The harder-when-brighter behavior in the X-ray spectra and the measured positive X-ray/VHE correlation during the 2009 multi-wavelength campaign suggests that the physical processes dominating the emission during non-flaring states have similarities with those occurring during flaring activity. In particular, this observation supports leptonic scenarios as being responsible for the emission of Mrk 421 during non-flaring activity. Such a temporally extended X-ray/VHE correlation is not driven by any single flaring event, and hence is difficult to explain within the standard hadronic scenarios. The highest variability is observed in the X-ray band, which, within the one-zone synchrotron self-Compton scenario, indicates that the electron energy distribution is most variable at the highest energies. Appendix A is available in electronic form at http://www.aanda.orgThe complete data set shown in Fig. 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/576/A126Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/69573eng(c) Springer Verlag, 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855022017-05-23T04:25:06Zhdl_2072_169514The variability plane of accreting compact objectsKörding, E. G.Migliari, SimoneFender, R. P.Belloni, T.Knigge, C.McHardy, I.Forats negres (Astronomia)Galàxies activesEstels binaris de raigs XBlack holes (Astronomy)Active galaxiesX-ray binariesRecently, it has been shown that soft-state black hole X-ray binaries and active galactic nuclei populate a plane in the space defined by the black hole mass, accretion rate and characteristic frequency. We show that this plane can be extended to hard-state objects if one allows a constant offset for the frequencies in the soft and the hard state. During a state transition, the frequencies rapidly move from one scaling to the other depending on an additional parameter, possibly the disc fraction. The relationship among frequency, mass and accretion rate can be further extended by including weakly accreting neutron stars (NSs). We explore if the lower kHz quasi-periodic oscillations of NSs and the dwarf nova oscillations of white dwarfs can be included as well and discuss the physical implications of the found correlation.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/99497eng(c) Körding, E. G. et al., 2007info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2664922017-05-23T04:25:11Zhdl_2072_169514Robust neutrino constraints by combining low redshift observations with the CMBReid, B. A.Verde, LiciaJiménez, Raúl (Jiménez Tellado)Mena, O.CosmologiaNeutrinsSupernovesCosmologyNeutrinosSupernovaeWe illustrate how recently improved low-redshift cosmological measurements can tighten constraints on neutrino properties. In particular we examine the impact of the assumed cosmological model on the constraints. We first consider the new HST H0 = 74.2±3.6 measurement by Riess et al. (2009) and the σ8(Ωm/0.25)0.41 = 0.832±0.033 constraint from Rozo et al. (2009) derived from the SDSS maxBCG Cluster Catalog. In a ΛCDM model and when combined with WMAP5 constraints, these low-redshift measurements constrain ∑mν < 0.4 eV at the 95% confidence level. This bound does not relax when allowing for the running of the spectral index or for primordial tensor perturbations. When adding also Supernovae and BAO constraints, we obtain a 95% upper limit of ∑mν < 0.3eV. We test the sensitivity of the neutrino mass constraint to the assumed expansion history by both allowing a dark energy equation of state parameter w≠−1 and by studying a model with coupling between dark energy and dark matter, which allows for variation in w, Ωk, and dark coupling strength ξ. When combining CMB, H0 and the SDSS LRG halo power spectrum from Reid et al. 2009, we find that in this very general model, ∑mν < 0.51 eV with 95% confidence. If we allow the number of relativistic species Nrel to vary in a ΛCDM model with ∑mν = 0, we find Nrel = 3.76+0.63−0.68(+1.38−1.21) for the 68% and 95% confidence intervals. We also report prior-independent constraints, which are in excellent agreement with the Bayesian constraints.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/101141eng(c) IOP Publishing Ltd and Sissa Medialab srl, 2010info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2839322017-05-23T04:25:41Zhdl_2072_169514On post-inflation validity of perturbation theory in Horndeski scalar-tensor modelsGermani, CristianoKudryashova, NinaWatanabe, YukiCosmologia quànticaRelativitat general (Física)Partícules (Física nuclear)Quantum cosmologyGeneral relativity (Physics)Particles (Nuclear physics)By using the newtonian gauge, we re-confirm that, as in the minimal case, the re-scaled Mukhanov-Sasaki variable is conserved leading to a constraint equation for the Newtonian potential. However, conversely to the minimal case, in Horndeski theories, the super-horizon Newtonian potential can potentially grow to very large values after inflation exit. If that happens, inflationary predictability is lost during the oscillating period. When this does not happen, the perturbations generated during inflation can be standardly related to the CMB, if the theory chosen is minimal at low energies. As a concrete example, we analytically and numerically discuss the new Higgs inflationary case. There, the Inflaton is the Higgs boson that is non-minimally kinetically coupled to gravity. During the high-energy part of the post-inflationary oscillations, the system is anisotropic and the Newtonian potential is largely amplified. Thanks to the smallness of today's amplitude of curvature perturbations, however, the system stays in the linear regime, so that inflationary predictions are not lost. At low energies, when the system relaxes to the minimal case, the anisotropies disappear and the Newtonian potential converges to a constant value. We show that the constant value to which the Newtonian potential converges is related to the frozen part of curvature perturbations during inflation, precisely like in the minimal case.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/110183eng(c) IOP Publishing Ltd and Sissa Medialab srl, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3030292018-01-04T06:29:05Zhdl_2072_169514Dynamics of Carroll stringsCardona Rotger, BielGomis Torné, JoaquimPons Ràfols, Josep MariaBosonsSimetria (Física)BosonsSymmetry (Physics)We construct the canonical action of a Carroll string doing the Carroll limit of a canonical relativistic string. We also study the Killing symmetries of the Carroll string, which close under an infinite dimensional algebra. The tensionless limit and the Carroll p-brane action are also discussed.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/118827engcc-by (c) Cardona Rotger, Biel et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3045182018-01-25T06:27:56Zhdl_2072_169514Stellar matter with pseudoscalar condensatesAndrianov, Alexander A.Andrianov, V. A.Espriu, D. (Domènec)Kolevatov, S. S.MatèriaAstrofísicaMatterAstrophysicsIn this work we consider how the appearance of gradients of pseudoscalar condensates in dense systems may possibly influence the transport properties of photons in such a medium as well as other thermodynamic characteristics. We adopt the hypothesis that in regions where the pseudoscalar density gradient is large the properties of photons and fermions are governed by the usual lagrangian extended with a Chern-Simons interaction for photons and a constant axial field for fermions. We find that these new pieces in the lagrangian produce non-trivial reflection coefficients both for photons and fermions when entering or leaving a region where the pseudoscalar has a non-zero gradient. A varying pseudoscalar density may also lead to instability of some fermion and boson modes and modify some properties of the Fermi sea. We speculate that some of these modifications could influence the cooling rate of stellar matter (for instance in compact stars) and have other observable consequences. While quantitative results may depend on the precise astrophysical details most of the consequences are quite universal and consideration should be given to this possibility.Società Italiana di Fisica & Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119255engcc-by (c) Andrianov, Alexander A. et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3044582018-01-25T06:28:02Zhdl_2072_169514Discrepancies between CFHTLenS cosmic shear and Planck: new physics or systematic effects?Kitching, Thomas D.Verde, LiciaHeavens, Alan F.Jiménez, Raúl (Jiménez Tellado)CosmologiaFísica còsmicaCosmologyCosmic physicsThere is currently a discrepancy in the measured value of the amplitude of matter clustering, parametrized using sigma(8), inferred from galaxy weak lensing, and cosmic microwave background (CMB) data, which could be an indication of new physics, such as massive neutrinos or a modification to the gravity law, or baryon feedback. In this paper we make the assumption that the cosmological parameters are well determined by Planck, and use weak lensing data to investigate the implications for baryon feedback and massive neutrinos, as well as possible contributions from intrinsic alignments and biases in photometric redshifts. We apply a nonparametric approach to model the baryonic feedback on the dark matter clustering, which is flexible enough to reproduce the OWLS (OverWhelmingly Large Simulations) and Illustris simulation results. The statistic we use, 3D cosmic shear, is a method that extracts cosmological information from weak lensing data using a spherical-Bessel function power spectrum approach. We analyse the CFHTLenS weak lensing data and, assuming best-fitting cosmological parameters from the Planck CMB experiment, find that there is no evidence for baryonic feedback on the dark matter power spectrum, but there is evidence for a bias in the photometric redshifts in the CFHTLenS data, consistent with a completely independent analysis by Choi et al., based on spectroscopic redshifts, and that these conclusions are robust to assumptions about the intrinsic alignment systematic. We also find an upper limit, of <0.28 eV (1 sigma), to the sum of neutrino masses conditional on other Lambda-cold-dark-matter parameters being fixed.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119237eng(c) Kitching, Thomas D. et al., 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3045202018-01-30T06:30:01Zhdl_2072_169514Metals in the z ∼ 3 intergalactic medium: results from an ultra-high signal-to-noise ratio UVES quasar spectrumD'Odorico, V.Cristiani, S.Pomante, E.Carswell, R. F.Viel, M.Barai, P.Becker, G. D.Calura, F.Cupani, G.Fontanot, F.Haehnelt, M. G.Kim, T.-S.Miralda Escudé, JordiRorai, A.Tescari, E.Vanzella, E.GalàxiesQuàsarsCosmologiaGalaxiesQuasarsCosmologyIn this work, we investigate the abundance and distribution of metals in the intergalactic medium (IGM) at 〈z〉 ≃ 2.8 through the analysis of an ultra-high signal-to-noise ratio UVES spectrum of the quasar HE0940-1050. In the C IV forest, our deep spectrum is sensitive at 3σ to lines with column density down to log NCIV ≃ 11.4 and in 60 per cent of the considered redshift range down to ≃11.1. In our sample, all H I lines with log NHI ≥ 14.8 show an associated C IV absorption. In the range 14.0 ≤ log NHI < 14.8, 43 per cent of H I lines has an associated C IV absorption. At log NHI < 14.0, the detection rates drop to <10 per cent, possibly due to our sensitivity limits and not to an actual variation of the gas abundance properties. In the range log NHI ≥ 14, we observe a fraction of H I lines with detected C IV a factor of 2 larger than the fraction of H I lines lying in the circumgalactic medium (CGM) of relatively bright Lyman-break galaxies hosted by dark matter haloes with 〈M〉 ∼ 1012 M⊙. The comparison of our results with the output of a grid of photoionization models and of two cosmological simulations implies that the volume filling factor of the IGM gas enriched to a metallicity logZ/Z⊙≳−3 logZ/Z⊙≳−3 should be of the order of ∼10-13 per cent. In conclusion, our results favour a scenario in which metals are found also outside the CGM of bright star-forming galaxies, possibly due to pollution by lower mass objects and/or to an early enrichment by the first sources.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119259eng(c) D'Odorico, V. et al., 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3056882018-02-14T06:29:22Zhdl_2072_169514Few-particle systems: An analysis of some strongly correlated statesBarberán Falcón, NúriaTaron i Roca, JosepConstitució de la matèriaMatèria condensadaConstitution of matterCondensed matterThe analysis of the quantum Hall response of a small system of interacting ultracold bosonic atoms through the variation of its Hall resistivity against the applied gauge magnetic field provides a powerful method to unmask its strongly correlated states in a quite exhaustive way. Within a fixed range of vaues of the magnetic field in the lowest Landau-level regime, where the resistivity displays two succesive plateaux, we identify the implied states as the Pfaffian and the state with filling factor \nu=2/3 in the thermodinamic limit. We fix the conditions to have good observability.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119795eng(c) American Physical Society, 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3056892018-02-14T06:29:22Zhdl_2072_169514Hyperporphyrin effects extended into a Jaggregate supramolecular structure in waterZurita, AdriánDuran, AnnaRibó i Trujillo, Josep M.El Hachemi, ZoubirCrusats i Aliguer, JoaquimPorfirinesEspectroscòpiaPorphyrinsSpectrum analysisThe relationship between the acid-base chemistry and the supramolecular behavior of 5-(4-aminophenyl)-10,15,20-tris(4-sulfonatophenyl)porphyrin in acidic water is reported. A new species exhibiting a prominently red-shifted Q-absorption band at 742 nm is described which is in accordance with a hyperporphyrin-type spectrum of a J-aggregate in water. UV-vis spectroscopy and peak force microscopy reveal that depending on the pH value of the medium the porphyrin self-assembles into two structurally different mesophases which can be reversibly interconverted at will.Royal Society of ChemistryUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119800engcc-by (c) Zurita, Adrián et al., 2017info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3048282018-02-15T06:35:37Zhdl_2072_169514Observation of B¯→D(*) π+π−ℓ−ν¯ Decays in e+e− Collisions at the Υ(4S) ResonanceGraugés Pous, EugeniBABAR CollaborationPartícules (Física nuclear)Mesons (Física nuclear)Particles (Nuclear physics)Mesons (Nuclear physics)We report on measurements of the decays of ¯ B mesons into the semileptonic final states ¯ B → D ( * ) π + π − ℓ − ¯ ν , where D ( * ) represents a D or D ∗ meson and ℓ − is an electron or a muon. These measurements are based on 471 × 10 6 B ¯ B pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R ( * ) π + π − = B ( ¯ B → D ( * ) π + π − ℓ − ¯ ν ) / B ( ¯ B → D ( * ) ℓ − ¯ ν ) using events in which the second B meson is fully reconstructed. We find R π + π − = 0.067 ± 0.010 ± 0.008 and R ∗ π + π − = 0.019 ± 0.005 ± 0.004 , where the first uncertainty is statistical and the second is systematic. Based on these results and assuming isospin invariance, we estimate that ¯ B → D ( * ) π π ℓ − ¯ ν decays, where π denotes either a π ± and π 0 meson, account for up to half the difference between the measured inclusive semileptonic branching fraction to charm hadrons and the corresponding sum of previously measured exclusive branching fractions.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119383eng(c) American Physical Society, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2668192018-02-20T06:32:09Zhdl_2072_169514Efficient reconstruction of linear baryon acoustic oscillations in galaxy surveysBurden, AngelaPercival, W.J.Manera, MarcCuesta, Antonio J.Vargas Magana, MarianaHo, ShirleyObservacions astronòmiquesCosmologiaAstronomical observationsCosmologyReconstructing an estimate of linear baryon acoustic oscillations (BAO) from an evolved galaxy field has become a standard technique in recent analyses. By partially removing non-linear damping caused by bulk motions, the real-space BAO peak in the correlation function is sharpened, and oscillations in the power spectrum are visible to smaller scales. In turn these lead to stronger measurements of the BAO scale. Future surveys are being designed assuming that this improvement has been applied, and this technique is therefore of critical importance for future BAO measurements. A number of reconstruction techniques are available, but the most widely used is a simple algorithm that decorrelates large-scale and small-scale modes approximately removing the bulk-flow displacements by moving the overdensity field. We consider the practical implementation of this algorithm, looking at the efficiency of reconstruction as a function of the assumptions made for the bulk-flow scale, the shot-noise level in a random catalogue used to quantify the mask and the method used to estimate the bulk-flow shifts. We also examine the efficiency of reconstruction against external factors including galaxy density, volume and edge effects, and consider their impact for future surveys. Throughout we make use of the mocks catalogues created for the Baryon Oscillation Spectroscopic Survey (BOSS) Date Release 11 samples covering 0.43 < z < 0.7 (CMASS) and 0.15 < z < 0.43 (LOWZ), to empirically test these changes.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/101837eng(c) Burden, Angela et al., 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3065692018-03-15T06:32:07Zhdl_2072_169514Running vacuum in the Universe and the time variation of the fundamental constants of NatureFritzsch, HaraldSolà Peracaula, JoanNunes, Rafael C.Matèria fosca (Astronomia)Partícules (Matèria)Dark matter (Astronomy)ParticlesWe compute the time variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine-structure constant and Newton's constant) within the context of the so-called running vacuum models (RVMs) of the cosmic evolution. Recently, compelling evidence has been provided that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance ΛCDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level ≳3σ. Here we use such remarkable status of the RVMs to make definite predictions on the cosmic time variation of the fundamental constants. It turns out that the predicted variations are close to the present observational limits. Furthermore, we find that the time evolution of the dark matter particle masses should be crucially involved in the total mass variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the 'micro-macro connection' (viz. the dynamical feedback between the evolution of the cosmological parameters and the time variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).Società Italiana di Fisica & Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/120598engcc-by (c) Fritzsch, Harald et al., 2017info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3067632018-03-16T06:26:56Zhdl_2072_169514Hyperporphyrin effects estended into a J-aggregate supramolecular structure in waterZurita, AdriánDuran, AnnaRibó i Trujillo, Josep M.El Hachemi, ZoubirCrusats i Aliguer, JoaquimEspectroscòpiaMicroscòpiaAiguaSpectrum analysisMicroscopyWaterThe relationship between the acid-base chemistry and the supramolecular behavior of 5-(4-aminophenyl)-10,15,20-tris(4-sulfonatophenyl)porphyrin in acidic water is reported. A new species exhibiting a prominently red-shifted Q-absorption band at 742 nm is described which is in accordance with a hyperporphyrin-type spectrum of a J-aggregate in water. UV-vis spectroscopy and peak force microscopy reveal that depending on the pH value of the medium the porphyrin self-assembles into two structurally different mesophases which can be reversibly interconverted at will.Royal Society of ChemistryUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/120780engcc-by (c) Zurita, Adrián et al., 2017info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3070132018-03-24T06:29:07Zhdl_2072_169514HfS, Hyperfine Structure Fitting ToolEstalella, RobertMolèculesEstructura molecularMoleculesMolecular structureHyperfine Structure Fitting (HfS) is a tool to fit the hyperfine structure of spectral lines with multiple velocity components. The HfS_nh3 procedures included in HfS simultaneously fit the hyperfine structure of the NH3 (J, K) = (1, 1) and (2, 2) transitions, and perform a standard analysis to derive ${T}_{\mathrm{ex}}$, NH3 column density, ${T}_{\mathrm{rot}}$, and ${T}_{{\rm{k}}}$. HfS uses a Monte Carlo approach for fitting the line parameters. Special attention is paid to the derivation of the parameter uncertainties. HfS includes procedures that make use of parallel computing for fitting spectra from a data cube.Astronomical Society of the PacificUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/121016eng(c) Estalella, Robert, 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2383472018-04-21T05:28:44Zhdl_2072_169514Cherenkov mesons as in-medium quark energy lossCasalderrey Solana, JorgeFernández, Daniel (Fernández Moreno)Mateos, David (Mateos Solé)HolografiaQuarksCamps de galga (Física)Cromodinàmica quànticaHolographyQuarksGauge fields (Physics)Quantum chromodynamicsWe recently showed that a heavy quark moving sufficiently fast through a quark-gluon plasma may lose energy by Cherenkov-radiating mesons [1]. Here we review our previous holographic calculation of the energy loss in N=4 Super Yang-Mills and extend it to longitudinal vector mesons and scalar mesons. We also discuss phenomenological implications for heavy-ion collision experiments. Although the Cherenkov energy loss is an O(1/Nc) effect, a ballpark estimate yields a value of dE/dx for Nc=3 which is comparable to that of other mechanisms.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/56368engcc by, (c) Casalderrey et al., 2010info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/">http://creativecommons.org/licenses/by/3.0/</a>
oai:recercat.cat:2072/3075652018-04-21T05:28:45Zhdl_2072_169514Phase Transitions, Inhomogeneous Horizons and Second-Order HydrodynamicsAttems, MaximilianBea, YagoCasalderrey Solana, JorgeMateos, David (Mateos Solé)Triana Iglesias, MiquelZilhão, MiguelForats negres (Astronomia)HolografiaHidrodinàmicaBlack holes (Astronomy)HolographyHydrodynamicsWe use holography to study the spinodal instability of a four-dimensional, strongly-coupled gauge theory with a first-order thermal phase transition. We place the theory on a cylinder in a set of homogeneous, unstable initial states. The dual gravity configurations are black branes afflicted by a Gregory-Laflamme instability. We numerically evolve Einstein's equations to follow the instability until the system settles down to a stationary, inhomogeneous black brane. The dual gauge theory states have constant temperature but non-constant energy density. We show that the time evolution of the instability and the final states are accurately described by second-order hydrodynamics. In the static limit, the latter reduces to a single, second-order, non-linear differential equation from which the inhomogeneous final states can be derived.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/121742engcc-by (c) Attems, Maximilian et al., 2017info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/1695712020-02-14T14:27:48Zhdl_2072_169514Constraints on effective field theory parameters for the Lambda N -> NN transitionPerez Obiol, AxelParreño García, AssumptaJuliá-Díaz, BrunoFísica nuclearReaccions nuclearsNuclear physicsNuclear reactionsThe relation between the low-energy constants appearing in the effective field theory description of the Lambda N -> NN transition potential and the parameters of the one-meson-exchange model previously developed is obtained. We extract the relative importance of the different exchange mechanisms included in the meson picture by means of a comparison to the corresponding operational structures appearing in the effective approach. The ability of this procedure to obtain the weak baryon-baryon-meson couplings for a possible scalar exchange is also discussed.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/19682eng(c) American Physical Society, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2812882020-02-14T14:27:49Zhdl_2072_169514First evidence for the annihilation decay mode B+→D+sϕAbellan Beteta, CarlosCalvo Gómez, MíriamCamboni, AlessandroComerma Montells, AlbertDomingo Bonal, FrancescGarrido Beltrán, LluísGrabalosa Gándara, MarcGraciani Díaz, RicardoGraugés Pous, EugeniLópez Asamar, EliasPérez-Calero Yzquierdo, AntonioPicatoste Olloqui, EduardoPie Valls, B. (Blai)Potterat, CédricRives Molina, Vicente JoséRuiz, Hugo (Ruiz Pérez)Vázquez Gómez, RicardVilasis-Cardona, XavierLHCb CollaborationInteraccions d'hadronsHadronsFísica nuclearDetectors de radiacióHadron interactionsHadronsNuclear physicsNuclear countersEvidence for the hadronic annihilation decay mode B+→D+sϕ is found with greater than 3σ significance. The branching fraction and CP asymmetry are measured to be $ B(B+→D+sϕ)=(1.87+1.25−0.73(stat)±0.19(syst)±0.32(norm))×10−6,ACP(B+→D+sϕ)=−0.01±0.41(stat)±0.03(syst). $ The last uncertainty on B(B+→D+sϕ) is from the branching fractions of the B+→D+sD¯¯¯0 normalization mode and intermediate resonance decays. Upper limits are also set for the branching fractions of the related decay modes B+(c)→D+(s)K∗0,B+(c)→D+(s)K¯¯¯∗0 and B+c→D+sϕ , including the result B(B+→D+K∗0)<1.8×10−6 at the 90% credibility level.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/56403engcc by, (c) LHCb Collaboration, 2013info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/">http://creativecommons.org/licenses/by/3.0/</a>
oai:recercat.cat:2072/3044592020-02-14T14:27:50Zhdl_2072_169514The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: baryon acoustic oscillations in the correlation function of LOWZ and CMASS galaxies in Data Release 12Cuesta, Antonio J.Vargas-Magana, MarianaBeutler, FlorianBolton, Adam S.Brownstein, Joel R.Eisenstein, Daniel J.Gil-Marin, HectorHo, ShirleyMcBride, Cameron K.Maraston, ClaudiaPadmanabhan, NikhilPercival, Will J.Reid, Beth A.Ross, Ashley J.Ross, Nicholas P.Sanchez, Ariel G.Schlegel, David J.Schneider, Donald P.Thomas, DanielTinker, Jeremy L.Tojeiro, RitaVerde, LiciaWhite, MartinCúmuls de galàxiesExpansió de l'universClusters of galaxiesExpanding universeWe present distance scale measurements from the baryon acoustic oscillation signal in the constant stellar mass and low-redshift sample samples from the Data Release 12 of the Baryon Oscillation Spectroscopic Survey. The total volume probed is 14.5 Gpc(3), a 10 per cent increment from Data Release 11. From an analysis of the spherically averaged correlation function, we infer a distance to z = 0.57 of Mpc and a distance to z = 0.32 of Mpc assuming a cosmology in which Mpc. From the anisotropic analysis, we find an angular diameter distance to z = 0.57 of Mpc and a distance to z = 0.32 of 981 +/- 20 Mpc, a 1.5 and 2.0 per cent measurement, respectively. The Hubble parameter at z = 0.57 is km s(-1) Mpc(-1) and its value at z = 0.32 is 79.2 +/- 5.6 km s(-1) Mpc(-1), a 3.7 and 7.1 per cent measurement, respectively. These cosmic distance scale constraints are in excellent agreement with a I > cold dark matter model with cosmological parameters released by the recent Planck 2015 results.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119239eng(c) Cuesta, Antonio J. et al., 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3045272020-02-14T14:27:50Zhdl_2072_169514The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: mock galaxy catalogues for the BOSS Final Data ReleaseKitaura, Francisco-ShuRodriguez-Torres, SergioChuang, Chia-HsunZhao, ChengPrada, FranciscoGil Marín, HéctorGuo, HongYepes, GustavoKlypin, AnatolyScoccola, Claudia G.Tinker, Jeremy L.McBride, CameronReid, BethSanchez, Ariel G.Salazar-Albornoz, SalvadorNiklas Grieb, JanVargas-Magana, MarianaCuesta, Antonio J.Neyrinck, MarkBeutler, FlorianComparat, JohanPercival, Will J.Ross, AshleyCúmuls de galàxiesUniversClusters of galaxiesUniverseWe reproduce the galaxy clustering catalogue from the SDSS-III Baryon Oscillation Spectroscopic Survey Final Data Release (BOSS DR11&DR12) with high fidelity on all relevant scales in order to allow a robust analysis of baryon acoustic oscillations and redshift space distortions. We have generated (6000) 12 288 MultiDark PATCHY BOSS (DR11) DR12 light cones corresponding to an effective volume of ¿192 000 [h-1 Gpc]3 (the largest ever simulated volume), including cosmic evolution in the redshift range from 0.15 to 0.75. The mocks have been calibrated using a reference galaxy catalogue based on the halo abundance matching modelling of the BOSS DR11&DR12 galaxy clustering data and on the data themselves. The production follows three steps. First, we apply the PATCHY code to generate a dark matter field and an object distribution including non-linear stochastic galaxy bias. Secondly, we run the halo/stellar distribution reconstruction HADRON code to assign masses to the various objects. This step uses the mass distribution as a function of local density and non-local indicators (i.e. tidal field tensor eigenvalues and relative halo exclusion separation for massive objects) from the reference simulation applied to the corresponding patchy dark matter and galaxy distribution. Finally, we apply the SUGAR code to build the light cones. The resulting MultiDarkPATCHY mock light cones reproduce the number density, selection function, survey geometry, and in general within 1σ, for arbitrary stellar mass bins, the power spectrum up to k = 0.3 h Mpc-1, the two-point correlation functions down to a few Mpc scales, and the three-point statistics of the BOSS DR11&DR12 galaxy samples.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119250eng(c) Kitaura, F.-S. et al., 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3045172020-02-14T14:27:51Zhdl_2072_169514The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: single-probe measurements from CMASS anisotropic galaxy clusteringChuang, Chia-HsunPrada, FranciscoPellejero Ibanez, MarcosBeutler, FlorianCuesta, Antonio J.Eisenstein, Daniel J.Escoffier, StephanieHo, ShirleyKitaura, Francisco-ShuKneib, Jean-PaulManera, MarcNuza, Sebastian E.Rodriguez Torres, SergioRoss, AshleyRubino Martin, J. A.Samushia, LadoSchlegel, David J.Schneider, Donald P.Wang, YutingWeaver, Benjamin A.Zhao, Gong-BoBrownstein, Joel R.Dawson, Kyle S.Maraston, ClaudiaOlmstead, Matthew D.Thomas, DanielCosmologiaUniversCúmuls de galàxiesCosmologyUniverseClusters of galaxiesWith the largest spectroscopic galaxy survey volume drawn from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), we can extract cosmological constraints from the measurements of redshift and geometric distortions at quasi-linear scales (e.g. above 50 $h^{-1}$Mpc). We analyze the broad-range shape of the monopole and quadrupole correlation functions of the BOSS Data Release 12 (DR12) CMASS galaxy sample, at the effective redshift $z=0.59$, to obtain constraints on the Hubble expansion rate $H(z)$, the angular-diameter distance $D_A(z)$, the normalized growth rate $f(z)\sigma_8(z)$, and the physical matter density $\Omega_mh^2$. We obtain robust measurements by including a polynomial as the model for the systematic errors, and find it works very well against the systematic effects, e.g., ones induced by stars and seeing. We provide accurate measurements $\{D_A(0.59)r_{s,fid}/r_s$ $\rm Mpc$, $H(0.59)r_s/r_{s,fid}$ $km s^{-1} Mpc^{-1}$, $f(0.59)\sigma_8(0.59)$, $\Omega_m h^2\}$ = $\{1427\pm26$, $97.3\pm3.3$, $0.488 \pm 0.060$, $0.135\pm0.016\}$, where $r_s$ is the comoving sound horizon at the drag epoch and $r_{s,fid}=147.66$ Mpc is the sound scale of the fiducial cosmology used in this study. The parameters which are not well constrained by our galaxy clustering analysis are marginalized over with wide flat priors. Since no priors from other data sets, e.g., cosmic microwave background (CMB), are adopted and no dark energy models are assumed, our results from BOSS CMASS galaxy clustering alone may be combined with other data sets, i.e., CMB, SNe, lensing or other galaxy clustering data to constrain the parameters of a given cosmological model. The uncertainty on the dark energy equation of state parameter, $w$, from CMB+CMASS is about 8 per cent. The uncertainty on the curvature fraction, $\Omega_k$, is 0.3 per cent. We do not find deviation from flat $\Lambda$CDM.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119253eng(c) Chuang, C. H. et al., 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3045192020-02-14T14:27:51Zhdl_2072_169514Large-scale clustering of Lyman α emission intensity from SDSS/BOSSCroft, Rupert A. C.Miralda Escudé, JordiZheng, ZhengBolton, Adam S.Dawson, Kyle S.Peterson, Jeffrey B.York, Donald G.Eisenstein, Daniel J.Brinkmann, JonBrownstein, Joel R.Cen, RenyueDelubac, TimotheeFont-Ribera, AndreuHamilton, Jean-ChristopheLee, Khee-GanMyers, AdamPalanque-Delabrouille, NathaliePâris, IsabellePetitjean, PatrickPieri, Matthew M.Ross, Nicholas P.Rossi, GrazianoSchlegel, David J.Schneider, Donald P.Slosar, AnzeVazquez, JoséViel, MatteoWeinberg, David H.Yèche, ChristopheCosmologiaGalàxiesCosmologyGalaxiesWe present a tentative detection of the large-scale structure of Ly α emission in the Universe at redshifts z = 2-3.5 by measuring the cross-correlation of Ly α surface brightness with quasars in Sloan Digital Sky Survey/Baryon Oscillation Spectroscopic Survey. We use a million spectra targeting luminous red galaxies at z < 0.8, after subtracting a best-fitting model galaxy spectrum from each one, as an estimate of the high-redshift Ly α surface brightness. The quasar-Ly α emission cross-correlation is detected on scales 1 ∼ 15 h−1 Mpc, with shape consistent with a ΛCDM model with Ωm=0.30+0.10−0.07 Ωm=0.30−0.07+0.10. The predicted amplitude of this cross-correlation is proportional to the product of the mean Ly α surface brightness, 〈μα〉, the amplitude of mass fluctuations and the quasar and Ly α emission bias factors. We infer 〈μα〉 (bα/3) = (3.9 ± 0.9) × 10−21 erg s−1 cm−2 Å−1 arcsec−2, where bα is the Ly α emission bias. If star-forming galaxies dominate this emission, we find ρSFR = (0.28 ± 0.07)(3/bα) yr−1 Mpc−3. For bα = 3, this value is ∼30 times larger than previous estimates from individually detected Ly α emitters, but consistent with the total ρSFR derived from dust-corrected, continuum UV galaxy surveys, if most of the Ly α photons from these galaxies avoid dust absorption and are reemitted after diffusing in large gas haloes. Heating of intergalactic gas by He II photoionization from quasar radiation or jets may alternatively explain the detected correlation, and cooling radiation from gas in galactic haloes may also contribute. We also detect redshift space anisotropy of the quasar-Ly α emission cross-correlation, finding evidence at the 3.0σ level that it is radially elongated, which may be explained by radiative-transfer effects. Our measurements represent the first application of the intensity mapping technique to optical observations.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119258eng(c) Croft, R. A. C. et al., 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3045212020-02-14T14:27:51Zhdl_2072_169514Beyond ΛCDM: Problems, solutions, and the road aheadBull, PhilipAkrami, YasharAdamek, JulianBaker, TessaBellini, EmilioBeltrán Jiménez, JoséBentivegna, EloisaCamera, StefanoClesse, SebastienDavis, Jonathan H.Di Dio, EneaEnander, JonasHeavens, AlanHeisenberg, LaviniaHu, BinLlinares, ClaudioMaartens, RoyMörtsell, EdvardNadathur, SeshadriNoller, JohannesPasechnik, RomanPawlowski, Marcel S.Pereira, Thiago S.Quartin, MiguelRicciardone, AngeloRiemer-Sørensen, SigneRinaldi, MassimilianoSakstein, JeremySaltas, Ippocratis D.Salzano, VincenzoSawicki, IgnacySolomon, Adam R.Spolyar, DouglasStarkman, Glenn D.Steer, DanieleTereno, IsmaelVerde, LiciaVillaescusa-Navarro, Franciscovon Strauss, MikaelWinther, Hans A.CosmologiaMatèria fosca (Astronomia)CosmologyDark matter (Astronomy)Despite its continued observational successes, there is a persistent (and growing) interest in extending cosmology beyond the standard model, ΛCDM. This is motivated by a range of apparently serious theoretical issues, involving such questions as the cosmological constant problem, the particle nature of dark matter, the validity of general relativity on large scales, the existence of anomalies in the CMB and on small scales, and the predictivity and testability of the inflationary paradigm. In this paper, we summarize the current status of ΛCDM as a physical theory, and review investigations into possible alternatives along a number of different lines, with a particular focus on highlighting the most promising directions. While the fundamental problems are proving reluctant to yield, the study of alternative cosmologies has led to considerable progress, with much more to come if hopes about forthcoming high-precision observations and new theoretical ideas are fulfilled.ElsevierUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/119262engcc-by-nc-nd (c) Elsevier, 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by-nc-nd/3.0/es">http://creativecommons.org/licenses/by-nc-nd/3.0/es</a>
oai:recercat.cat:2072/3532782020-02-14T14:27:52Zhdl_2072_169514A precise measurement of the B-0 meson oscillation frequencyGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationMesons (Física nuclear)Oscil·lacionsMesons (Nuclear physics)OscillationsThe oscillation frequency, Delta m(d), of B-0 mesons is measured using semileptonic decays with a D- or D*(-) meson in the final state. The data sample corresponds to 3.0 fb(-1) of pp collisions, collected by the LHCb experiment at centre-of-mass energies root s = 7 and 8 TeV. A combination of the two decay modes gives Delta m(d) = (505.0 +/- 2.1 +/- 1.0) ns(-1), where the first uncertainty is statistical and the second is systematic. This is the most precise single measurement of this parameter. It is consistent with the current world average and has similar precision.Società Italiana di Fisica & Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119268engcc-by (c) LHCb collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3045242020-02-14T14:27:52Zhdl_2072_169514Amplitude analysis of B- →d+π-π- decaysCamboni, AlessandroGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséBadalov, AlexeyLHCb CollaborationRessonànciaPartícules (Física nuclear)ResonanceParticles (Nuclear physics)The Dalitz plot analysis technique is used to study the resonant substructures of B− → Dþπ−π− decays in a data sample corresponding to 3.0 fb−1 of pp collision data recorded by the LHCb experiment during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high Dþπ− mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the Dþπ− S wave together with virtual contributions from the Dð2007Þ0 and B0 states, and components corresponding to the D 2ð2460Þ0, D1ð2680Þ0, D3ð2760Þ0 and D2ð3000Þ0 resonances. The masses and widths of these resonances are determined together with the branching fractions for their production in B− → Dþπ−π− decays. The Dþπ− S wave has phase motion consistent with that expected due to the presence of the D0ð2400Þ0 state. These results constitute the first observations of the D3ð2760Þ0 and D2ð3000Þ0 resonances, with significances of 10σ and 6.6σ, respectively.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119269eng(c) American Physical Society, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3045252020-02-14T14:27:52Zhdl_2072_169514Angular analysis of the B0 → K*0μ+μ− decay using 3 fb−1 of integrated luminosityGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséBadalov, AlexeyLHCb CollaborationInteraccions d'hadronsPartícules (Física nuclear)Hadron interactionsParticles (Nuclear physics)An angular analysis of the B0 → K∗0 (→ K+π−)µ+µ− decay is presented. The dataset corresponds to an integrated luminosity of 3.0 fb−1 of pp collision data collected at the LHCb experiment. The complete angular information from the decay is used to determine CP-averaged observables and CP asymmetries, taking account of possible contamination from decays with the K+π− system in an S-wave configuration. The angular observables and their correlations are reported in bins of q2, the invariant mass squared of the dimuon system. The observables are determined both from an unbinned maximum likelihood fit and by using the principal moments of the angular distribution. In addition, by fitting for q2-dependent decay amplitudes in the region 1.1 < q2 < 6.0 GeV2/c4, the zero-crossing points of several angular observables are computed. A global fit is performed to the complete set of CP-averaged observables obtained from the maximum likelihood fit. This fit indicates differences with predictions based on the Standard Model at the level of 3.4 standard deviations. These differences could be explained by contributions from physics beyond the Standard Model, or by an unexpectedly large hadronic effect that is not accounted for in the Standard Model predictions.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119271engcc-by (c) LHCb collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3532792020-02-14T14:27:53Zhdl_2072_169514Differential branching fraction and angular moments analysis of the decay B 0 → K +π− μ + μ − in the K 0,2∗ (1430)0 regionCamboni, AlessandroGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséBadalov, AlexeyLHCb CollaborationInteraccions d'hadronsPartícules (Física nuclear)Hadron interactionsParticles (Nuclear physics)Measurements of the differential branching fraction and angular moments of the decay B 0 → K +π− μ + μ − in the K +π− invariant mass range 1330 < m(K +π−) < 1530 MeV/c 2 are presented. Proton-proton collision data are used, corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, q 2, between 0.1 and 8.0 GeV2 /c 4. For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the q 2 range 1.1-6.0 GeV2 /c 4.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119272engcc-by (c) LHCb collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3047132020-02-14T14:27:53Zhdl_2072_169514First observation of the decay B(formula presented.)at LHCbCasanova Mohr, RaimonGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRuiz, Hugo (Ruiz Pérez)Badalov, AlexeyLHCb CollaborationInteraccions d'hadronsCol·lisions (Física)Hadron interactionsCollisions (Physics)A search for B0 (s) → K0SK∗ (892)0 decays is performed using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected with the LHCb detector at a centre-of-mass energy of 7 TeV. The B0 s → K0 SK∗ (892)0 decay is observed for the first time, with a significance of 7.1 standard deviations. The branching fraction is measured to be B(B 0 s → K¯ 0K∗ (892)0 ) + B(B 0 s → K0K¯ ∗ (892)0 ) = (16.4 ± 3.4 ± 2.3) × 10−6 , where the first uncertainty is statistical and the second is systematic. No evidence is found for the decay B0 → K0 SK∗ (892)0 and an upper limit is set on the branching fraction, B(B0 → K¯ 0K∗ (892)0 ) + B(B0 → K0K¯ ∗ (892)0 ) < 0.96 × 10−6 , at 90 % confidence level. All results are consistent with Standard Model predictionsSpringer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119305engcc-by (c) LHCb collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3523862020-02-14T14:27:54Zhdl_2072_169514Differential branching fraction and angular analysis of the decay B 0 → K ∗0 μ + μ -Abellan Beteta, CarlosCalvo Gómez, MíriamCamboni, AlessandroComerma Montells, AlbertGarrido Beltrán, LluísGraciani Díaz, RicardoGraugés Pous, EugeniLópez Asamar, EliasOyanguren Campos, Arantza dePérez-Calero Yzquierdo, AntonioPicatoste Olloqui, EduardoPotterat, CédricRives Molina, Vicente JoséRuiz, Hugo (Ruiz Pérez)Ruiz Valls, PabloVázquez Gómez, RicardVilasis-Cardona, XavierLHCb CollaborationDetectors de radiacióCromodinàmica quànticaHadronsNuclear countersQuantum chromodynamicsHadronsThe angular distribution and differential branching fraction of the decay B 0→ K ∗0 μ + μ − are studied using a data sample, collected by the LHCb experiment in pp collisions at s√=7 TeV, corresponding to an integrated luminosity of 1.0 fb−1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/56443engcc by, (c) LHCb Collaboration, 2013info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/">http://creativecommons.org/licenses/by/3.0/</a>
oai:recercat.cat:2072/3532802020-02-14T14:27:54Zhdl_2072_169514Measurement of forward W → eν production in pp collisions at √s=8 TeVBadalov, AlexeyCamboni, AlessandroGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationInteraccions d'hadronsPartícules (Física nuclear)Hadron interactionsParticles (Nuclear physics)A measurement of the cross-section for W → eν production in pp collisions is presented using data corresponding to an integrated luminosity of 2 fb−1 collected by the LHCb experiment at a centre-of-mass energy of s√=8s=8 TeV. The electrons are required to have more than 20 GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive W production cross-sections, where the W decays to eν, are measured to be σW+→e+νe=1124.4±2.1±21.5±11.2±13.0pb, σW+→e+νe=1124.4±2.1±21.5±11.2±13.0pb, σW−→e−ν¯¯¯e=809.0±1.9±18.1±7.0±9.4pb, σW−→e−ν¯e=809.0±1.9±18.1±7.0±9.4pb, where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. Differential cross-sections as a function of the electron pseudorapidity are measured. The W + /W − cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of W boson branching fractions is determined to be B(W→eν)/B(W→μν)=1.020±0.002±0.019, B(W→eν)/B(W→μν)=1.020±0.002±0.019, where the first uncertainty is statistical and the second is systematic.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119339engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3047172020-02-14T14:27:55Zhdl_2072_169514Measurement of forward W and Z boson production in association with jets in proton-proton collisions at √s = 8 TeVGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationProtonsCol·lisions (Física)ProtonsCollisions (Physics)The production of W and Z bosons in association with jets is studied in the forward region of proton-proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 ± 0.02 fb−1. The W boson is identified using its decay to a muon and a neutrino, while the Z boson is identified through its decay to a muon pair. Total cross-sections are measured and combined into charge ratios, asymmetries, and ratios of W +jet and Z+jet production cross-sections. Differential measurements are also performed as a function of both boson and jet kinematic variables. All results are in agreement with Standard Model predictions.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119340engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3047182020-02-14T14:27:55Zhdl_2072_169514Measurement of forward W and Z boson production in pp collisions at (Formula Presented.) TeVGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationCol·lisions (Física)Interaccions d'hadronsCollisions (Physics)Hadron interactionsMeasurements are presented of electroweak boson production using data from pp collisions at a centre-of-mass energy of s√=8s=8 TeV. The analysis is based on an integrated luminosity of 2.0 fb−1 recorded with the LHCb detector. The bosons are identified in the W → μν and Z → μ + μ − decay channels. The cross-sections are measured for muons in the pseudorapidity range 2.0 < η < 4.5, with transverse momenta p T > 20 GeV/c and, in the case of the Z boson, a dimuon mass within 60<Mμ+μ−<12060<Mμ+μ−<120 GeV/c 2. The results are σW+→μ+ν=1093.6±2.1±7.2±10.9±12.7pb,σW−→μ−ν¯¯¯=818.4±1.9±5.0±7.0±9.5pb,σZ→μ+μ−=95.0±0.3±0.7±1.1±1.1pb, σW+→μ+ν=1093.6±2.1±7.2±10.9±12.7pb,σW−→μ−ν¯=818.4±1.9±5.0±7.0±9.5pb,σZ→μ+μ−=95.0±0.3±0.7±1.1±1.1pb, where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. The evolution of the W and Z boson cross-sections with centre-of-mass energy is studied using previously reported measurements with 1.0 fb−1 of data at 7 TeV. Differential distributions are also presented. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119341engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3047212020-02-14T14:27:56Zhdl_2072_169514Measurement of the CKM angle γ using B 0 → DK *0 with D → K S0 π + π − decaysBadalov, AlexeyGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationPartícules (Matèria)Interaccions d'hadronsParticlesHadron interactionsA model-dependent amplitude analysis of the decay B 0 → D(K S 0 π + π −)K ∗ 0 is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb−1, recorded at s√=7s=7 and 8 TeV by the LHCb experiment. The CP violation observables x ± and y ±, sensitive to the CKM angle γ, are measured to be x−=−0.15±0.14±0.03±0.01,y−=0.25±0.15±0.06±0.01,x+=0.05±0.24±0.04±0.01,y+=−0.65+0.24−0.23±0.08±0.01, x−=−0.15±0.14±0.03±0.01,y−=0.25±0.15±0.06±0.01,x+=0.05±0.24±0.04±0.01,y+=−0.65−0.23+0.24±0.08±0.01, where the first uncertainties are statistical, the second systematic and the third arise from the uncertainty on the D → K S 0 π + π − amplitude model. These are the most precise measurements of these observables. They correspond to γ = (80 − 22 + 21 )° and rB0=0.39±0.13rB0=0.39±0.13, where rB0rB0 is the magnitude of the ratio of the suppressed and favoured B 0 → DK + π − decay amplitudes, in a Kπ mass region of ±50 MeV around the K *(892)0 mass and for an absolute value of the cosine of the K *0 decay angle larger than 0.4.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119346engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3047222020-02-14T14:27:56Zhdl_2072_169514Measurement of the forward Z boson production cross-section in pp collisions at √s=13 TeVBadalov, AlexeyCamboni, AlessandroGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationInteraccions d'hadronsHadron interactionsA measurement of the production cross-section of Z bosons in pp collisions at s√=13s=13 TeV is presented using dimuon and dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range 2.0 < η < 4.5, transverse momenta p T > 20 GeV and dilepton invariant mass in the range 60 < m(ℓℓ) < 120 GeV. The integrated cross-section from averaging the two final states is σ Z ℓℓ = 194.3 ± 0.9 ± 3.3 ± 7.6 pb, where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable ϕ η * .Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119353engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3048242020-02-14T14:27:57Zhdl_2072_169514Measurement of the properties of the Ξb∗0 baryonBadalov, AlexeyGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationEspectroscòpiaInteraccions d'hadronsSpectrum analysisHadron interactionsWe perform a search for near-threshold Ξb 0 resonances decaying to Ξb −π+ in a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment. We observe one resonant state, with the following properties: (Formula presented.). This confirms the previous observation by the CMS collaboration. The state is consistent with the JP = 3/2+ Ξb ∗0 resonance expected in the quark model. This is the most precise determination of the mass and the first measurement of the natural width of this state. We have also measured the ratio (Formula presented.)Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119376engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3491592020-02-14T14:27:57Zhdl_2072_169514Measurements of prompt charm production cross-sections in pp collisions at √s = 13 TeVBadalov, AlexeyGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationInteraccions d'hadronsQuarksHadron interactionsQuarksProduction cross-sections of prompt charm mesons are measured with the first data from pp collisions at the LHC at a centre-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 4.98 ± 0.19 pb−1 collected by the LHCb experiment. The production cross-sections of D 0, D +, D s + , and D *+ mesons are measured in bins of charm meson transverse momentum, p T, and rapidity, y, and cover the range 0 < p T < 15GeV/c and 2.0 < y < 4.5. The inclusive cross-sections for the four mesons, including charge conjugation, within the range of 1 < p T < 8 GeV/c are found to be σ(pp→D0X)=2460±3±130μbσ(pp→D+X)=1000±3±110μbσ(pp→D+sX)=460±13±100μbσ(pp→D∗+X)=880±5±140μb σ(pp→D0X)=2460±3±130μbσ(pp→D+X)=1000±3±110μbσ(pp→Ds+X)=460±13±100μbσ(pp→D∗+X)=880±5±140μb where the uncertainties are due to statistical and systematic uncertainties, respectively.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119379engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3532812020-02-14T14:27:58Zhdl_2072_169514Measurements of the S-wave fraction in B 0 → K + π − μ + μ − decays and the B 0 → K ∗(892)0 μ + μ − differential branching fractionBadalov, AlexeyGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationInteraccions d'hadronsHadron interactionsA measurement of the differential branching fraction of the decay B 0 → K ∗(892)0 μ + μ − is presented together with a determination of the S-wave fraction of the K + π − system in the decay B 0 → K +π− μ + μ −. The analysis is based on pp-collision data corresponding to an integrated luminosity of 3 fb−1 collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, q 2. Precise theoretical predictions for the differential branching fraction of B 0 → K ∗(892)0 μ + μ − decays are available for the q 2 region 1.1 < q 2 < 6.0 GeV2 /c 4. In this q 2 region, for the K +π− invariant mass range 796 < m Kπ < 996 MeV/c 2, the S-wave fraction of the K +π− system in B 0 → K +π− μ + μ − decays is found to be FS=0.101±0.017(stat)±0.009(syst), FS=0.101±0.017(stat)±0.009(syst), and the differential branching fraction of B 0 → K ∗(892)0 μ + μ − decays is determined to be dB/dq2=(0.392+0.020−0.019(stat)±0.010(syst)±0.027(norm))×10−7c4/GeV2. dB/dq2=(0.392−0.019+0.020(stat)±0.010(syst)±0.027(norm))×10−7c4/GeV2. The differential branching fraction measurements presented are the most precise to date and are found to be in agreement with Standard Model predictions.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119380engcc by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3532822020-02-14T14:27:58Zhdl_2072_169514Model-independent measurement of the CKM angle γ using B0 → DK∗0 decays with D → K S0 π + π − and K S0 K+K−Badalov, AlexeyGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationInteraccions d'hadronsViolació CP (Física nuclear)Hadron interactionsCP violation (Nuclear physics)A binned Dalitz plot analysis of the decays B 0 → DK ∗0, with D → K S 0 π + π − and D → K S 0 K + K −, is performed to measure the observables x ± and y ±, which are related to the CKM angle γ and the hadronic parameters of the decays. The D decay strong phase variation over the Dalitz plot is taken from measurements performed at the CLEO-c experiment, making the analysis independent of the D decay model. With a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb experiment, the values of the CP violation parameters are found to be x + = 0.05 ± 0.35 ± 0.02, x − = −0.31 ± 0.20 ± 0.04, y + = −0.81 ± 0.28 ± 0.06 and y − = 0.31 ± 0.21 ± 0.05, where the first uncertainties are statistical and the second systematic. These observables correspond to values γ = (71 ± 20)°, rB0=0.56±0.17rB0=0.56±0.17 and δB0=(204+21−20)∘δB0=(204−20+21)∘ . The parameters rB0rB0 and δB0δB0 are the magnitude ratio and strong phase difference between the suppressed and favoured B 0 decay amplitudes, and have been measured in a region of ±50 MeV/c 2 around the K ∗(892)0 mass and with the magnitude of the cosine of the K ∗(892)0 helicity angle larger than 0.4.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119381engcc by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3048292020-02-14T14:27:59Zhdl_2072_169514Observation of the Bs0→ J/ψϕϕ decayGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséBadalov, AlexeyLHCb CollaborationInteraccions d'hadronsEspectroscòpiaHadron interactionsSpectrum analysisThe B s 0 → J/ψϕϕ decay is observed in pp collision data corresponding to an integrated luminosity of 3 fb−1 recorded by the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV. This is the first observation of this decay channel, with a statistical significance of 15 standard deviations. The mass of the B s 0 meson is measured to be 5367.08 ± 0.38 ± 0.15 MeV/c2. The branching fraction ratio ℬ(B s 0 → J/ψϕϕ)/ℬ(B s 0 → J/ψϕ) is measured to be 0.0115 ± 0.0012 − 0.0009 + 0.0005 . In both cases, the first uncertainty is statistical and the second is systematic. No evidence for non-resonant B s 0 → J/ψϕK + K − or B s 0 → J/ψK + K − K + K − decays is found.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119387engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2855032020-02-14T14:28:00Zhdl_2072_169514Differential Branching Fraction and Angular Analysis of the Decay B-0 -> K*(0)mu(+)mu(-)Abellan Beteta, CarlosCalvo Gómez, MíriamCamboni, AlessandroComerma Montells, AlbertDomingo Bonal, FrancescGarrido Beltrán, LluísGascón Fora, DavidGrabalosa Gándara, MarcGraciani Díaz, RicardoGraugés Pous, EugeniLópez Asamar, EliasMusy, MarcoPérez-Calero Yzquierdo, AntonioPicatoste Olloqui, EduardoPie Valls, B. (Blai)Potterat, CédricPuig Navarro, AlbertRoselló, M.Ruiz, Hugo (Ruiz Pérez)Vázquez Gómez, RicardVilasis-Cardona, XavierLHCb CollaborationDetectors de radiacióPartícules (Física nuclear)Nuclear countersParticles (Nuclear physics)The angular distributions and the partial branching fraction of the decay B0→K*0μ+μ− are studied by using an integrated luminosity of 0.37 fb−1 of data collected with the LHCb detector. The forward-backward asymmetry of the muons, AFB, the fraction of longitudinal polarization, FL, and the partial branching fraction dB/dq2 are determined as a function of the dimuon invariant mass. The measurements are in good agreement with the standard model predictions and are the most precise to date. In the dimuon invariant mass squared range 1.00-6.00 GeV2/c4, the results are AFB=−0.06+0.13−0.14±0.04, FL=0.55±0.10±0.03, and dB/dq2=(0.42±0.06±0.03)×10−7 c4/GeV2. In each case, the first error is statistical and the second systematic.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/56447engcc by (c) LHCb Collaboration, 2012info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/">http://creativecommons.org/licenses/by/3.0/</a>
oai:recercat.cat:2072/3049072020-02-14T14:28:00Zhdl_2072_169514Observation of Λb0→ ψ(2S)pK−and Λb0→ J/ψπ+π−pK−decays and a measurement of the Λb0baryon massGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséBadalov, AlexeyLHCb CollaborationInteraccions d'hadronsEspectroscòpiaHadron interactionsSpectrum analysisThe decays Λ b 0 → ψ(2S)pK− and Λ b 0 → J/ψπ + π −pK− are observed in a data sample corresponding to an integrated luminosity of 3 fb−1, collected in proton-proton collisions at 7 and 8 TeV centre-of-mass energies by the LHCb detector. The ψ(2S) mesons are reconstructed through the decay modes ψ(2S) → μ+μ− and ψ(2S) → J/ψπ + π −. The branching fractions relative to that of Λ b 0 → J/ψpK− are measured to be B(Λ0b→ψ(2S)pK−)B(Λ0b→J/ψpK−)=(20.70±0.76±0.46±0.37)×10−2, B(Λb0→ψ(2S)pK−)B(Λb0→J/ψpK−)=(20.70±0.76±0.46±0.37)×10−2, where the first uncertainties are statistical, the second are systematic and the third is related to the knowledge of J/ψ and ψ(2S) branching fractions. The mass of the Λ b 0 baryon is measured to be M(Λ0b)=5619.65±0.17±0.17 MeV/c2, M(Λb0)=5619.65±0.17±0.17 MeV/c2, where the uncertainties are statistical and systematic.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119399engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3049082020-02-14T14:28:01Zhdl_2072_169514Production of associated Y and open charm hadrons in pp collisions at ∔s = 7 and 8 TeV via double parton scatteringGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséBadalov, AlexeyLHCb CollaborationInteraccions d'hadronsQuarksHadron interactionsQuarksAssociated production of bottomonia and open charm hadrons in pp collisions at s√=7s=7 and 8 TeV is observed using data corresponding to an integrated luminosity of 3 fb−1 accumulated with the LHCb detector. The observation of five combinations, Y(1S)D0, Y(2S)D0, Y(1S)D+, Y(2S)D+ and Y(1S)D s + , is reported. Production crosssections are measured for Y(1S)D0 and Y(1S)D+ pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119407engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3049102020-02-14T14:28:01Zhdl_2072_169514Search for Higgs-like bosons decaying into long-lived exotic particlesBadalov, AlexeyGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationPartícules (Matèria)Bosons de HiggsParticlesHiggs bosonsA search is presented for massive long-lived particles, in the 20-60 GeV/c2GeV/c2 mass range with lifetimes between 5 and 100 psps . The dataset used corresponds to 0.62 fb −1 fb −1 of proton-proton collision data collected by the LHCb detector at s√=7TeVs=7TeV . The particles are assumed to be pair-produced by the decay of a Higgs-like boson with mass between 80 and 140 GeV/c2GeV/c2 . No excess above the background expectation is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime and of the Higgs-like boson mass.Società Italiana di Fisica & Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119418engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3051362020-02-14T14:28:02Zhdl_2072_169514The Clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: combining correlated Gaussian posterior distributionsSanchez, Ariel G.Grieb, Jan NiklasSalazar-Albornoz, SalvadorAlam, ShadabBeutler, FlorianRoss, Ashley J.Brownstein, Joel R.Chuang, Chia-HsunCuesta, Antonio J.Eisenstein, Daniel J.Kitaura, Francisco-ShuPercival, Will J.Prada, FranciscoRodríguez-Torres, SergioSeo, Hee-JongTinker, Jeremy L.Tojeiro, RitaVargas-Magaña, MarianaVazquez, Jose A.Zhao, Gong-BoCúmuls de galàxiesCosmologiaClusters of galaxiesCosmologyThe cosmological information contained in anisotropic galaxy clustering measurements can often be compressed into a small number of parameters whose posterior distribution is well described by a Gaussian. We present a general methodology to combine these estimates into a single set of consensus constraints that encode the total information of the individual measurements, taking into account the full covariance between the different methods. We illustrate this technique by applying it to combine the results obtained from different clustering analyses, including measurements of the signature of baryon acoustic oscillations (BAO) and redshift-space distortions (RSD), based on a set of mock catalogues of the final SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Our results show that the region of the parameter space allowed by the consensus constraints is smaller than that of the individual methods, highlighting the importance of performing multiple analyses on galaxy surveys even when the measurements are highly correlated. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The methodology presented here is used in Alam et al. (2016) to produce the final cosmological constraints from BOSS.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119500eng(c) Sanchez, A. G. et al., 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3051372020-02-14T14:28:03Zhdl_2072_169514The Clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: baryon acoustic oscillations in the Fourier spaceBeutler, FlorianSeo, H. J.Ross, A. J.McDonald, P.Saito, S.Bolton, Adam S.Brownstein, Joel R.Chuang, Chia-HsunCuesta, Antonio J.Eisenstein, Daniel J.Font-Ribera, A.Grieb, J. N.Hand, NickKitaura, F. S.Modi, C.Nichol, R. C.Percival, W. J.Prada, F.Rodriguez-Torres, S.Roe, N. A.Ross, N. P.Salazar-Albornoz, S.Sánchez, A. G.Schneider, D. P.Slosar, A.Tinker, Jeremy L.Tojeiro, R.Vargas-Magaña, M.Vazquez, J. A.Cúmuls de galàxiesEspectroscòpiaClusters of galaxiesSpectrum analysisWe analyse the Baryon Acoustic Oscillation (BAO) signal of the final Baryon Oscillation Spectroscopic Survey (BOSS) data release (DR12). Our analysis is performed in Fourier-space, using the power spectrum monopole and quadrupole. The dataset includes $1\,198\,006$ galaxies over the redshift range $0.2 < z < 0.75$. We divide this dataset into three (overlapping) redshift bins with the effective redshifts $\zeff = 0.38$, $0.51$ and $0.61$. We demonstrate the reliability of our analysis pipeline using N-body simulations as well as $\sim 1000$ MultiDark-Patchy mock catalogues, which mimic the BOSS-DR12 target selection. We apply density field reconstruction to enhance the BAO signal-to-noise ratio. By including the power spectrum quadrupole we can separate the line-of-sight and angular modes, which allows us to constrain the angular diameter distance $D_A(z)$ and the Hubble parameter $H(z)$ separately. We obtain two independent $1.6\%$ and $1.5\%$ constraints on $D_A(z)$ and $2.9\%$ and $2.3\%$ constraints on $H(z)$ for the low ($\zeff=0.38$) and high ($\zeff=0.61$) redshift bin, respectively. We obtain two independent $1\%$ and $0.9\%$ constraints on the angular averaged distance $D_V(z)$, when ignoring the Alcock-Paczynski effect. The detection significance of the BAO signal is of the order of $8\sigma$ (post-reconstruction) for each of the three redshift bins. Our results are in good agreement with the Planck prediction within $\Lambda$CDM. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The measurements and likelihoods presented here are combined with others in~\citet{Alam2016} to produce the final cosmological constraints from BOSS.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119502eng(c) Beutler, F. et al., 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3711612020-02-14T14:28:03Zhdl_2072_169514First evidence of running cosmic vacuum: challenging the concordance modelSolà Peracaula, JoanGómez Valent, AdriàCruz Pérez, Javier deEnergia fosca (Astronomia)Matèria fosca (Astronomia)Dark energy (Astronomy)Dark matter (Astronomy)Despite the fact that a rigid Λ-term is a fundamental building block of the concordance ΛCDM model, we show that a large class of cosmological scenarios with dynamical vacuum energy density ρΛ and/or gravitational coupling G, together with a possible non-conservation of matter, are capable of seriously challenging the traditional phenomenological success of the ΛCDM. In this paper, we discuss these 'running vacuum models' (RVM's), in which ρΛ=ρΛ(H) consists of a nonvanishing constant term and a series of powers of the Hubble rate. Such generic structure is potentially linked to the quantum field theoretical description of the expanding Universe. By performing an overall fit to the cosmological observables SNIa+BAO+H(z)+LSS+BBN+CMB (in which the WMAP9, Planck 2013 and Planck 2015 data are taken into account), we find that the class of RVM's appears significantly more favored than the ΛCDM, namely at an unprecedented level of ≳4.2σ. Furthermore, the Akaike and Bayesian information criteria confirm that the dynamical RVM's are strongly preferred as compared to the conventional rigid Λ-picture of the cosmic evolution.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119632eng(c) American Astronomical Society, 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3055982020-02-14T14:28:04Zhdl_2072_169514The Clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: observational systematics and baryon acoustic oscillations in the correlation functionRoss, Ashley J.Beutler, FlorianChuang, Chia-HsunPellejero Ibanez, MarcosSeo, Hee-JongVargas Magaña, MarianaCuesta, Antonio J.Percival, Will J.Burden, AngelaSánchez, Ariel G.Grieb, Jan NiklasReid, BethBrownstein, Joel R.Dawson, Kyle S.Eisenstein, Daniel J.Ho, ShirleyKitaura, Francisco-ShuNichol, Robert C.Olmstead, Matthew D. OPrada, FranciscoRodríguez Torres, Sergio A.Saito, ShunSalazar-Albornoz, SalvadorSchneider, Donald P.Thomas, DanielTinker, Jeremy L.Tojeiro, RitaWang, YutingWhite, MartinZhao, Gong-BoCúmuls de galàxiesEspectroscòpiaClusters of galaxiesSpectrum analysisWe present baryon acoustic oscillation (BAO) scale measurements determined from the clustering of 1.2 million massive galaxies with redshifts 0.2 < z < 0.75 distributed over 9300 deg2, as quantified by their redshift-space correlation function. In order to facilitate these measurements, we define, describe, and motivate the selection function for galaxies in the final data release (DR12) of the SDSS III Baryon Oscillation Spectroscopic Survey (BOSS). This includes the observational footprint, masks for image quality and Galactic extinction, and weights to account for density relationships intrinsic to the imaging and spectroscopic portions of the survey. We simulate the observed systematic trends in mock galaxy samples and demonstrate that they impart no bias on BAO scale measurements and have a minor impact on the recovered statistical uncertainty. We measure transverse and radial BAO distance measurements in 0.2 < z < 0.5, 0.5 < z < 0.75, and (overlapping) 0.4 < z < 0.6 redshift bins. In each redshift bin, we obtain a precision that is 2.7 per cent or better on the radial distance and 1.6 per cent or better on the transverse distance. The combination of the redshift bins represents 1.8 per cent precision on the radial distance and 1.1 per cent precision on the transverse distance. This paper is part of a set that analyses the final galaxy clustering data set from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al. to produce the final cosmological constraints from BOSS.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119730eng(c) Ross, A. J. et al., 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3057272020-02-14T14:28:04Zhdl_2072_169514Constraining the thin disc initial mass function using Galactic classical CepheidsMor Crespo, RogerRobin, A. C.Figueras Siñol, FrancescaLemasle, B.Classificació dels estelsEvolució de les galàxiesStar ClassificationGalaxies evolutionContext: The Initial Mass Function (IMF) plays a crucial role on galaxy evolution and its implications on star formation theory make it a milestone for the next decade. It is in the intermediate and high mass ranges where the uncertainties of the IMF are larger. This is a major subject of debate and analysis both for Galactic and extragalactic science. Aims: Our goal is to constrain the IMF of the Galactic thin disc population using both Galactic Classical Cepheids and Tycho-2 data. Methods: For the first time the Besan\c{c}on Galaxy Model (BGM) has been used to characterise the Galactic population of the Classical Cepheids. We have modified the age configuration in the youngest populations of the BGM thin disc model to avoid artificial discontinuities in the age distribution of the simulated Cepheids. Three statistical methods, optimized for different mass ranges, have been developed and applied to search for the best IMF that fits the observations. This strategy allows us to quantify variations in the Star Formation History (SFH), the stellar density at Sun position and the thin disc radial scale length. A rigorous treatment of unresolved multiple stellar systems has been undertaken adopting a spatial resolution according to the catalogues used. Results: For intermediate masses, our study favours a composite field-star IMF slope of $\alpha=3.2$ for the local thin disc, excluding flatter values such as the Salpeter IMF ($\alpha=2.35$). Moreover, a constant Star Formation History is definitively excluded, the three statistical methods considered here show that it is inconsistent with the observational data. Conclusions: Using field stars and Galactic Classical Cepheids, we have found, above $1M_\odot$, an IMF steeper than the canonical stellar IMF of associations and young clusters. This result is consistent with the predictions of the Integrated Galactic IMF.EDP SciencesUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119831eng(c) The European Southern Observatory (ESO), 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3057282020-02-14T14:28:04Zhdl_2072_169514The young open cluster NGC 7067 using Str\'omgren photometryMonguió, M.Negueruela, I.Marco, A.González Fernández, C.Alonso Santiago, J.Costado, M. T.Casamiquela Floriach, LaiaLópez Corredoira, M.Molgó, J.Vilardell, F.Alfaro, E. J.Antoja Castelltort, M. TeresaFigueras Siñol, FrancescaGarcia, M.Jordi i Nebot, CarmeRomero Gómez, MercèFotometria astronòmicaEspectroscòpia astronòmicaAstronomical photometryAstronomical spectroscopyNGC 7067 is a young open cluster located in the direction between the first and the second Galactic quadrants and close to the Perseus spiral arm. This makes it useful for studies of the nature of the Milky Way spiral arms. Stromgren photometry taken with the Wide Field Camera at the Isaac Newton Telescope allowed us to compute individual physical parameters for the observed stars and hence to derive cluster's physical parameters. Spectra from the 1.93-m telescope at the Observatoire de Haute-Provence helped to check and improve the results. We obtained photometry for 1233 stars, individual physical parameters for 515 and spectra for 9 of them. The 139 selected cluster members lead to a cluster distance of 4.4+/-0.4 kpc, with an age below log10(t(yr))=7.3 and a present Mass of 1260+/-160Msun. The morphology of the data reveals that the centre of the cluster is at (ra,dec)=(21:24:13.69,+48:00:39.2) J2000, with a radius of 6.1arcsec. Stromgren and spectroscopic data allowed us to improve the previous parameters available for the cluster in the literature.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/119833eng(c) Monguió, M. et al., 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3711622020-02-14T14:28:04Zhdl_2072_169514A Search for Spectral Hysteresis and Energy-dependent Time Lags from X-Ray and TeV Gamma-Ray Observations of Mrk 421Galindo Fernández, DanielMarcote Martin, BenitoParedes i Poy, Josep MariaParedes Fortuny, XavierRibó Gomis, MarcTorres-Albà, N.Zanin, RobertaMAGIC CollaborationVERITAS CollaborationGalàxiesRaigs gammaGalaxiesGamma raysBlazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars simultaneously at different wavelengths, especially in the X-ray and gamma-ray bands, where the broadband spectral energy distributions usually peak. In this work, we report on three 'target-of-opportunity' observations of Mrk 421, one of the brightest TeV blazars, triggered by a strong flaring event at TeV energies in 2014. These observations feature long, continuous, and simultaneous exposures with XMM-Newton (covering the X-ray and optical/ultraviolet bands) and VERITAS (covering the TeV gamma-ray band), along with contemporaneous observations from other gamma-ray facilities (MAGIC and Fermi-Large Area Telescope) and a number of radio and optical facilities. Although neither rapid flares nor significant X-ray/TeV correlation are detected, these observations reveal subtle changes in the X-ray spectrum of the source over the course of a few days. We search the simultaneous X-ray and TeV data for spectral hysteresis patterns and time delays, which could provide insight into the emission mechanisms and the source properties (e.g., the radius of the emitting region, the strength of the magnetic field, and related timescales). The observed broadband spectra are consistent with a one-zone synchrotron self-Compton model. We find that the power spectral density distribution at gsim4 × 10−4 Hz from the X-ray data can be described by a power-law model with an index value between 1.2 and 1.8, and do not find evidence for a steepening of the power spectral index (often associated with a characteristic length scale) compared to the previously reported values at lower frequencies.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/120043eng(c) American Astronomical Society, 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2812902020-02-14T14:28:05Zhdl_2072_169514Differential branching fraction and angular analysis of the B+→K+μ+μ− decayAbellan Beteta, CarlosCalvo Gómez, MíriamCamboni, AlessandroComerma Montells, AlbertDomingo Bonal, FrancescGarrido Beltrán, LluísGrabalosa Gándara, MarcGraciani Díaz, RicardoGraugés Pous, EugeniLópez Asamar, EliasPérez-Calero Yzquierdo, AntonioPicatoste Olloqui, EduardoPie Valls, B. (Blai)Potterat, CédricRives Molina, Vicente JoséRuiz, Hugo (Ruiz Pérez)Vázquez Gómez, RicardVilasis-Cardona, XavierLHCb CollaborationGran Col·lisionador d'HadronsTeoria quàntica de campsRelativitat (Física)Partícules (Física nuclear)Large Hadron Collider (France and Switzerland)Quantum field theoryRelativity (Physics)Particles (Nuclear physics)The angular distribution and differential branching fraction of the decay B +→ K + μ + μ − are studied with a dataset corresponding to 1.0fb−1 of integrated luminosity, collected by the LHCb experiment. The angular distribution is measured in bins of dimuon invariant mass squared and found to be consistent with Standard Model expectations. Integrating the differential branching fraction over the full dimuon invariant mass range yields a total branching fraction of B (B + → K + μ + μ −) = (4.36 ± 0.15 ± 0.18) × 10−7. These measurements are the most precise to date of the B + → K + μ + μ − decay.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/56456engcc by, (c) LHCb Collaboration, 2013info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/">http://creativecommons.org/licenses/by/3.0/</a><a href="http://creativecommons.org/licenses/by/3.0/">http://creativecommons.org/licenses/by/3.0/</a>
oai:recercat.cat:2072/3062722020-02-14T14:28:05Zhdl_2072_169514Search for B+c decays to the ppπ+ final stateBadalov, AlexeyGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationMesons (Física nuclear)Massa (Física)Mesons (Nuclear physics)Mass (Physics)A search for the decays of the B+ c meson to pp¯π+ is performed for the first time using a data sample corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV. No signal is found and an upper limit, at 95 confidence level, is set, fc fu × B(B+ c → ppπ+) < 3.6 × 10−8 in the kinematic region m(pp) < 2.85 GeV/c2, pT(B) < 20 GeV/c and 2.0 < y(B) < 4.5, where B is the branching fraction and fc ( fu) is the fragmentation fraction of the b quark into a Bc+ (B+) meson.ElsevierUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/120257engcc-by (c) LHCb Collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3062732020-02-14T14:28:05Zhdl_2072_169514Measurement of the CKM angle from a combination of LHCb resultsBadalov, AlexeyCamboni, AlessandroCoquereau, S.Garrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationInteraccions d'hadronsPartícules (Física nuclear)Hadron interactionsParticles (Nuclear physics)A combination of measurements sensitive to the CKM angle γ from LHCb is performed. The inputs are from analyses of time-integrated B + → DK +, B 0 → DK ∗0, B 0 → DK +π− and B + → DK +π+π− tree-level decays. In addition, results from a time-dependent analysis of B s 0 → D s ∓ K ± decays are included. The combination yields γ = (72. 2 − 7.3 + 6.8 )°, where the uncertainty includes systematic effects. The 95.5% confidence level interval is determined to be γ ∈ [55.9, 85.2]°. A second combination is investigated, also including measurements from B + → Dπ+ and B + → Dπ+π−π+ decays, which yields compatible results.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/120260engcc-by (c) LHCb collaboration et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3073452020-02-14T14:28:05Zhdl_2072_169514Gaia data release 1, the photometric dataCarrasco Martínez, José ManuelFigueras Siñol, FrancescaJordi i Nebot, CarmeVoss, HölgerWeiler, MichaelBalaguer Núñez, María de los DoloresMasana Fresno, EduardFabricius, ClausGebran, M.Portell i de Mora, JordiTorra Roca, JorgeGaia CollaborationGalàxiesFotometria astronòmicaGalaxiesAstronomical photometryThis paper presents an overview of the photometric data that are part of the first Gaia data release. Aims. The principles of the processing and the main characteristics of the Gaia photometric data are presented. Methods. The calibration strategy is outlined briefly and the main properties of the resulting photometry are presented. Results. Relations with other broadband photometric systems are provided. The overall precision for the Gaia photometry is shown to be at the milli-magnitude level and has a clear potential to improve further in future releases.EDP SciencesUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/121416eng(c) The European Southern Observatory (ESO), 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3080042020-02-14T14:28:06Zhdl_2072_169514Beyond dimensional analysis: Higgs and new Higgs inflations do not violate unitarityGermani, CristianoEscrivà, AlbertCosmologia quànticaBosons de HiggsQuantum cosmologyHiggs bosonsNaive dimensional analysis seems to suggest possible unitarity violations in the framework of the Higgs and new Higgs inflationary scenarios. These violations seem to happen around the value in which the potential energy, per a given Higgs boson's vacuum expectation value, crosses the perturbative cutoff scale calculated around the electroweak vacuum. Conversely to these expectations, we show that, by using an exact analysis of the background dependent cutoff scale, and by including the contribution of the phase-space volume in the perturbative scattering amplitudes of scalars, no violation of (perturbative) unitarity might ever happen during the whole Universe evolution.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122140eng(c) American Physical Society, 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3711632020-02-14T14:28:06Zhdl_2072_169514Quantum correlations and degeneracy of identical bosons in a two-dimensional harmonic trapMujal Torreblanca, PereSarlé, EnricPolls Martí, ArturJuliá-Díaz, BrunoBosonsConstitució de la matèriaBosonsConstitution of matterWe consider a small number of identical bosons trapped in a two-dimensional isotropic harmonic potential and also the N-boson system when it is feasible. The atom-atom interaction is modeled by means of a finite-range Gaussian interaction. The spectral properties of the system are scrutinized and, in particular, we derive analytic expressions for the degeneracies and their breaking for the lower-energy states at small but finite interactions. We demonstrate that the degeneracy of the low-energy states is independent of the number of particles in the noninteracting limit and also for sufficiently weak interactions. In the strongly interacting regime, we show how the many-body wave function develops holes whenever two particles are at the same position in space to avoid the interaction, a mechanism reminiscent of the Tonks-Girardeau gas in one dimension. The evolution of the system as the interaction is increased is studied by means of the density profiles, pair correlations, and fragmentation of the ground state for 2, 3, and 4 bosons.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122368eng(c) American Physical Society, 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3503082020-02-14T14:28:06Zhdl_2072_169514Octet baryon magnetic moments from lattice QCD: Approaching experiment from a three-flavor symmetric pointParreño García, AssumptaSavage, Martin J.Tiburzi, Brian C.Wilhelm, JonasChang, EmmanuelDetmold, WilliamOrginos, KostasCromodinàmica quànticaCamps magnètics (Física còsmica)Quantum chromodynamicsCosmic magnetic fieldsLattice QCD calculations with background magnetic fields are used to determine the magnetic moments of the octet baryons. Computations are performed at the physical value of the strange quark mass, and two values of the light quark mass, one corresponding to the S U ( 3 ) F -symmetric point, where the pion mass is m π ∼ 800 MeV , and the other corresponding to a pion mass of m π ∼ 450 MeV . The moments are found to exhibit only mild pion-mass dependence when expressed in terms of appropriately chosen magneton units the natural baryon magneton. A curious pattern is revealed among the anomalous baryon magnetic moments which is linked to the constituent quark model, however, careful scrutiny exposes additional features. Relations expected to hold in the large- N c limit of QCD are studied; and, in one case, a clear preference for the quark model over the large- N c prediction is found. The magnetically coupled Λ - Σ 0 system is treated in detail at the S U ( 3 ) F point, with the lattice QCD results comparing favorably with predictions based on S U ( 3 ) F symmetry. This analysis enables the first extraction of the isovector transition magnetic polarizability. The possibility that large magnetic fields stabilize strange matter is explored, but such a scenario is found to be unlikely.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122381eng(c) American Physical Society, 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3215782020-02-14T14:28:07Zhdl_2072_169514A model for the repeating FRB 121102 in the AGN scenarioVieyro, F. L.Romero, G. E.Bosch i Ramon, ValentíMarcote Martin, BenitoValle, M. V. delGalàxies activesCosmologiaActive galaxiesCosmologyContext. Fast radio bursts (FRBs) are transient sources of unknown origin. Recent radio and optical observations have provided strong evidence for an extragalactic origin of the phenomenon and the precise localization of the repeating FRB 121102. Observations using the Karl G. Jansky Very Large Array (VLA) and very-long-baseline interferometry (VLBI) have revealed the existence of a continuum non-thermal radio source consistent with the location of the bursts in a dwarf galaxy. All these new data rule out several models that were previously proposed, and impose stringent constraints to new models. Aims. We aim to model FRB 121102 in light of the new observational results in the active galactic nucleus (AGN) scenario. Methods. We propose a model for repeating FRBs in which a non-steady relativistic e±-beam, accelerated by an impulsive magnetohydrodynamic driven mechanism, interacts with a cloud at the centre of a star-forming dwarf galaxy. The interaction generates regions of high electrostatic field called cavitons in the plasma cloud. Turbulence is also produced in the beam. These processes, plus particle isotropization, the interaction scale, and light retardation effects, provide the necessary ingredients for short-lived, bright coherent radiation bursts. Results. The mechanism studied in this work explains the general properties of FRB 121102, and may also be applied to other repetitive FRBs. Conclusions. Coherent emission from electrons and positrons accelerated in cavitons provides a plausible explanation of FRBs.EDP SciencesUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122384eng(c) The European Southern Observatory (ESO), 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3138882020-02-14T14:28:07Zhdl_2072_169514A study of the association of Fermi sources with massive young galactic objectsMunar i Adrover, PereParedes i Poy, Josep MariaRomero, G. E.EstelsRaigs gammaStarsGamma raysMassive protostars have associated bipolar outflows that can produce strong shocks when they interact with the surrounding medium. At these shocks particles can be accelerated up to relativistic energies. Relativistic electrons and protons can then produce gamma-ray emission, as some theoretical models predict. To identify young galactic objects that may emit gamma rays, we crossed the Fermi First Year Catalog with some catalogs of known massive young stellar objects (MYSOs), early type stars, and OB associations, and we implemented Monte Carlo simulations to find the probability of chance coincidences. We obtained a list of massive MYSOs that are spatially coincident with Fermi sources. Our results indicate that \sim 70% of these candidates should be gamma-ray sources with a confidence of \sim 5{\sigma}. We studied the coincidences one by one to check the viability of these young sources as potential counterparts to Fermi sources and made a short list of best targets for new detailed multifrequency observations. The results for other type of young galactic objects are not conclusive.EDP SciencesUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122716eng(c) The European Southern Observatory (ESO), 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3138892020-02-14T14:28:07Zhdl_2072_169514Gamma-ray excess from a stacked sample of high-frequency peaked blazars observed with the MAGIC telescopeParedes i Poy, Josep MariaBosch i Ramon, ValentíBordas Coma, PolMoldón Vara, Francisco JavierZabalza de Torres, VíctorRibó Gomis, MarcRaigs gammaGalàxiesGamma raysGalaxiesBetween 2004 and 2009, a sample of 28 X-ray selected high- and intermediate-frequency peaked blazars with an X-ray flux larger than 2 μJy at 1 keV in the redshift range from 0.018 to 0.361 was observed with the MAGIC telescope at energies above 100 GeV. Seven among them were detected and the results of these observations are discussed elsewhere. Here we concentrate on the remaining 21 blazars which were not detected during this observation campaign and present the 3σ (99.7%) confidence upper limits on their flux. The individual flux upper limits lie between 1.6% and 13.6% of the integral flux from the Crab Nebula. Applying a stacking method to the sample of non-detections with a total of 394.1 hr exposure time, we find evidence for an excess with a cumulative significance of 4.9 standard deviations. It is not dominated by individual objects or flares, but increases linearly with the observation time as for a constant source with an integral flux level of ~1.5% of that observed from the Crab Nebula above 150 GeV.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122725eng(c) American Astronomical Society, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3214932020-02-14T14:28:08Zhdl_2072_169514On the origin of correlated X-ray/VHE emission from LS I +61 303Zabalza de Torres, VíctorParedes i Poy, Josep MariaBosch i Ramon, ValentíEstels binaris de raigs XRadiacióX-ray binariesRadiationThe MAGIC collaboration has recently reported correlated X-ray and very high-energy gamma-ray emission from the gamma-ray binary LS I +61 303 during ~60% of one orbit. These observations suggest that the emission in these two bands has its origin in a single particle population. We aim at improving our understanding of the source behaviour by explaining the simultaneous X-ray and VHE data through a radiation model. We use a model based on a one zone population of relativistic leptonic particles assuming dominant adiabatic losses located at the position of the compact object. The adiabatic cooling timescale is inferred from the X-ray fluxes. The model can reproduce the spectra and lightcurves in the X-ray and VHE bands. Adiabatic losses could be the key ingredient to explain the X-ray and partially the VHE lightcurves. From the best fit result, we obtain a magnetic field of B=0.2 G, a minimum luminosity budget of ~2x10^35 erg/s and a relatively high acceleration efficiency. In addition, our results seem to confirm that the GeV emission detected by Fermi does not come from the same parent particle population as the X-ray and VHE emission and the Fermi spectrum poses a constraint on the hardness of the particle spectrum at lower energies. In the context of our scenario, more sensitive observations would allow to constrain the inclination angle, which could determine the nature of the compact object.EDP SciencesUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122811eng(c) The European Southern Observatory (ESO), 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2812912020-02-14T14:28:08Zhdl_2072_169514Differential branching fraction and angular analysis of the decay B_s^0 → ϕμ + μ -Abellan Beteta, CarlosCalvo Gómez, MíriamCamboni, AlessandroComerma Montells, AlbertGarrido Beltrán, LluísGraciani Díaz, RicardoGraugés Pous, EugeniLópez Asamar, EliasOyanguren Campos, Arantza dePérez-Calero Yzquierdo, AntonioPicatoste Olloqui, EduardoPotterat, CédricRives Molina, Vicente JoséRuiz, Hugo (Ruiz Pérez)Ruiz Valls, PabloVázquez Gómez, RicardVilasis-Cardona, XavierLHCb CollaborationGran Col·lisionador d'HadronsCromodinàmica quànticaHadronsDetectors de radiacióLarge Hadron Collider (France and Switzerland)Quantum chromodynamicsHadronsNuclear countersThe determination of the differential branching fraction and the first angular analysis of the decay B0s → ϕμ + μ − are presented using data, corresponding to an integrated luminosity of 1.0 fb−1, collected by the LHCb experiment at s√=7 TeV. The differential branching fraction is determined in bins of q 2, the invariant dimuon mass squared. Integration over the full q 2 range yields a total branching fraction of B(B0s→ϕμ+μ−)=(7.07+0.64−0.59±0.71±0.71) × 10−7, where the first uncertainty is statistical, the second systematic, and the third originates from the branching fraction of the normalisation channel. An angular analysis is performed to determine the angular observables F L, S 3, A 6, and A 9. The observables are consistent with Standard Model expectations.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/56464engcc by, (c) LHCb Collaboration, 2013info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/">http://creativecommons.org/licenses/by/3.0/</a>
oai:recercat.cat:2072/3214942020-02-14T14:28:08Zhdl_2072_169514Observations of the blazar 3C 66A with the magic telescopes in stereoscopic modeParedes i Poy, Josep MariaBordas Coma, PolBosch i Ramon, ValentíRibó Gomis, MarcCañellas, A.Moldón Vara, Francisco JavierZabalza de Torres, VíctorGalàxies activesRaigs gammaActive galaxiesGamma raysWe report new observations of the intermediate-frequency peaked BL Lacertae object 3C 66A with the MAGIC telescopes. The data sample we use were taken in 2009 December and 2010 January, and comprises 2.3 hr of good quality data in stereoscopic mode. In this period, we find a significant signal from the direction of the blazar 3C 66A. The new MAGIC stereoscopic system is shown to play an essential role for the separation between 3C 66A and the nearby radio galaxy 3C 66B, which is at a distance of only 6'. The derived integral flux above 100 GeV is 8.3% of the Crab Nebula flux and the energy spectrum is reproduced by a power law of photon index 3.64 ± 0.39stat ± 0.25sys. Within errors, this is compatible with the one derived by VERITAS in 2009. From the spectra corrected for absorption by the extragalactic background light, we only find small differences between the four models that we applied, and constrain the redshift of the blazar to z < 0.68.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122812eng(c) American Astronomical Society, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3214952020-02-14T14:28:09Zhdl_2072_169514Insights into the High-energy γ-ray Emission of Markarian 501 from Extensive Multifrequency Observations in the Fermi EraBordas Coma, PolBosch i Ramon, ValentíMoldón Vara, Francisco JavierParedes i Poy, Josep MariaRibó Gomis, MarcZabalza de Torres, VíctorAcceleradors de partículesGalàxiesRaigs gammaParticle acceleratorsGalaxiesGamma raysWe report on the γ-ray activity of the blazar Mrk501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) -ray spectrum of Mrk501 can be well described by a single power-law function with a photon index of 1.78 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 0.14, and the softest one is 2.51 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15August 1) on Mrk501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size r0.1pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (C1044ergs1) constitutes only a small fraction (<103) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122813eng(c) American Astronomical Society, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3215792020-02-14T14:28:09Zhdl_2072_169514Spectral energy distribution of Markarian 501: quiescent state versus extreme outburstParedes i Poy, Josep MariaBosch i Ramon, ValentíRibó Gomis, MarcMoldón Vara, Francisco JavierBordas Coma, PolZabalza de Torres, VíctorGalàxies activesRaigs XRaigs gammaActive galaxiesX-raysGamma raysThe very high energy (VHE; E > 100 GeV) blazar Markarian 501 has a well-studied history of extreme spectral variability and is an excellent laboratory for studying the physical processes within the jets of active galactic nuclei. However, there are few detailed multiwavelength studies of Markarian 501 during its quiescent state, due to its low luminosity. A short-term multiwavelength study of Markarian 501 was coordinated in March 2009, focusing around a multi-day observation with the Suzaku X-ray satellite and including {\gamma}-ray data from VERITAS, MAGIC, and the Fermi Gamma-ray Space Telescope with the goal of providing a well-sampled multiwavelength baseline measurement of Markarian 501 in the quiescent state. The results of these quiescent-state observations are compared to the historically extreme outburst of April 16, 1997, with the goal of examining variability of the spectral energy distribution between the two states. The derived broadband spectral energy distribution shows the characteristic double-peaked profile. We find that the X-ray peak shifts by over two orders of magnitude in photon energy between the two flux states while the VHE peak varies little. The limited shift in the VHE peak can be explained by the transition to the Klein-Nishina regime. Synchrotron self-Compton models are matched to the data and the implied Klein-Nishina effects are explored.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122835eng(c) American Astronomical Society, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3215802020-02-14T14:28:09Zhdl_2072_169514MAGIC Discovery of Very High Energy Emission from the FSRQ PKS 1222+21Paredes i Poy, Josep MariaMoldón Vara, Francisco JavierRibó Gomis, MarcZabalza de Torres, VíctorCañellas, A.Raigs còsmicsGalàxies activesQuàsarsCosmic raysActive galaxiesQuasarsVery High Energy (VHE) gamma-ray emission from the flat spectrum radio quasar (FSRQ) PKS 1222+21 (4C 21.35, z=0.432) was detected with the MAGIC Cherenkov telescopes during a short observation (~0.5 hr) performed on 2010 June 17. The MAGIC detection coincides with high energy MeV/GeV gamma-ray activity measured by the Large Area Telescope (LAT) on board the Fermi satellite. The VHE spectrum measured by MAGIC extends from about 70 GeV up to at least 400 GeV and can be well described by a power law dN/dE \propto E^-Gamma with a photon index Gamma= 3.75+/-0.27stat +/-0.2syst. The averaged integral flux above 100 GeV is (4.56+/-0.46)x10^(-10) cm^-2 s^-1 (~1 Crab Nebula flux). The VHE flux measured by MAGIC varies significantly within the 30 min exposure implying a flux doubling time of about 10 min. The VHE and MeV/GeV spectra, corrected for the absorption by the extragalactic background light (EBL), can be described by a single power law with photon index 2.72+/-0.34 between 3 GeV and 400 GeV, and is consistent with emission belonging to a single component in the jet. The absence of a spectral cutoff constrains the gamma-ray emission region outside the Broad Line Region, which would otherwise absorb the VHE gamma-rays. Together with the detected fast variability, this challenges present emission models from jets in FSRQ. Moreover, the combined Fermi/LAT and MAGIC spectral data yield constraints on the density of the Extragalactic Background Light in the UV-optical to near-infrared range that are compatible with recent models.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122837eng(c) American Astronomical Society, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3215812020-02-14T14:28:09Zhdl_2072_169514A search for Very High Energy gamma-ray emission from Sco X-1 with the MAGIC telescopesBordas Coma, PolBosch i Ramon, ValentíCañellas, A.Moldón Vara, Francisco JavierMunar i Adrover, PereParedes i Poy, Josep MariaRibó Gomis, MarcZabalza de Torres, VíctorAcceleradors de partículesEstels binaris de raigs XRaigs XParticle acceleratorsX-ray binariesX-raysThe acceleration of particles up to GeV or higher energies in microquasars has been the subject of considerable theoretical and observational efforts in the past few years. Sco X-1 is a microquasar from which evidence of highly energetic particles in the jet has been found when it is in the so-called Horizontal Branch (HB), a state when the radio and hard X-ray fluxes are higher and a powerful relativistic jet is present. Here we present the first very high energy gamma-ray observations of Sco X-1 obtained with the MAGIC telescopes. An analysis of the whole dataset does not yield a significant signal, with 95% CL flux upper limits above 300 GeV at the level of 2.4x10^{-12} ph/cm^2/s. Simultaneous RXTE observations were conducted to search for TeV emission during particular X-ray states of the source. A selection of the gamma-ray data obtained during the HB based on the X-ray colors did not yield a signal either, with an upper limit of 3.4x10^{-12} ph/cm^2/s. These upper limits place a constraint on the maximum TeV luminosity to non-thermal X-ray luminosity of L_{VHE}/L_{ntX}<0.02, that can be related to a maximum TeV luminosity to jet power ratio of L_{VHE}/L_{j}<10^{-3}. Our upper limits indicate that the underlying high-energy emission physics in Sco X-1 must be inherently different from that of the hitherto detected gamma-ray binaries.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122838eng(c) American Astronomical Society, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3215822020-02-14T14:28:10Zhdl_2072_169514Fermi large area telescope observations of Markarian 421: the missing piece of its spectral energy distributionBordas Coma, PolBosch i Ramon, ValentíMoldón Vara, Francisco JavierParedes i Poy, Josep MariaRibó Gomis, MarcZabalza de Torres, VíctorAcceleradors de partículesGalàxies activesRaigs gammaParticle acceleratorsActive galaxiesGamma raysWe report on the gamma-ray activity of the high-synchrotron-peaked BL Lacertae object Mrk 421 during the first 1.5 years of Fermi operation, from 2008 August 5 to 2010 March 12. We find that the Large Area Telescope (LAT) gamma-ray spectrum above 0.3 GeV can be well-described by a power-law function with photon index Gamma=1.78 +/- 0.02 and average photon flux F(>0.3 GeV)=(7.23 +/- 0.16) x 10^{-8} ph cm^{-2} s^{-1}. Over this time period, the Fermi-LAT spectrum above 0.3 GeV was evaluated on 7-day-long time intervals, showing significant variations in the photon flux (up to a factor ~3 from the minimum to the maximum flux), but mild spectral variations. The variability amplitude at X-ray frequencies measured by RXTE/ASM and Swift/BAT is substantially larger than that in gamma-rays measured by Fermi-LAT, and these two energy ranges are not significantly correlated. We also present the first results from the 4.5-month-long multifrequency campaign on Mrk 421, which included the VLBA, Swift, RXTE, MAGIC, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign (2009 January 19 to 2009 June 1). During this campaign, Mrk 421 showed a low activity at all wavebands. The extensive multi-instrument (radio to TeV) data set provides an unprecedented, complete look at the quiescent spectral energy distribution (SED) for this source. The broad band SED was reproduced with a leptonic (one-zone Synchrotron Self-Compton) and a hadronic model (Synchrotron Proton Blazar). Both frameworks are able to describe the average SED reasonably well, implying comparable jet powers but very different characteristics for the blazar emission site.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122841eng(c) American Astronomical Society, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3215832020-02-14T14:28:10Zhdl_2072_169514Revealing the extended radio emission from the gamma-ray binary HESS J0632+057Moldón Vara, Francisco JavierRibó Gomis, MarcParedes i Poy, Josep MariaEstels binaris de raigs XRaigs gammaX-ray binariesGamma raysAfter the detection of a 321-days periodicity in X-rays, HESS J0632+057 can be robustly considered a new member of the selected group of gamma-ray binaries. These sources are known to show extended radio structure at scales of milliarcseconds (mas). Aims. We present the expected extended radio emission on mas scales from HESS J0632+057. Methods. We observed HESS J0632+057 with the European VLBI Network (EVN) at 1.6 GHz in two epochs: during the January/February 2011 X-ray outburst and 30 days later. Results. The VLBI image obtained during the outburst shows a compact ~0.4 mJy radio source, whereas 30 days later the source has faded and appears extended, with a projected size of ~75 AU. The peak of the emission is displaced between runs 21+/-5 AU, which is bigger than the orbit size. The position of the radio source is compatible with the Be star MWC 148, which sets the proper motion of the binary system below 3 mas yr^-1 in each coordinate. The brightness temperature of the source is above 2 \times 10^6 K. We compare the multiwavelength properties of HESS J0632+057 with those of the previously known gamma-ray binaries. Conclusions. HESS J0632+057 displays extended and variable non-thermal radio emission. Its morphology, size, and displacement at AU scales are similar to those found in the other gamma-ray binaries, PSR B1259-63, LS 5039 and LS I +61 303, supporting a similar nature for HESS J0632+057.EDP SciencesUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122842eng(c) The European Southern Observatory (ESO), 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3215842020-02-14T14:28:10Zhdl_2072_169514Observations of the Crab Pulsar between 25 and 100 GeV with the MAGIC I TelescopeCañellas, A.Marcote Martin, BenitoMunar i Adrover, PereMoldón Vara, Francisco JavierParedes i Poy, Josep MariaRibó Gomis, MarcZabalza de Torres, VíctorEstelsRaigs gammaStarsGamma raysWe report on the observation of $\gamma$-rays above 25\,GeV from the Crab pulsar (PSR B0532+21) using the MAGIC I telescope. Two data sets from observations during the winter period 2007/2008 and 2008/2009 are used. In order to discuss the spectral shape from 100\,MeV to 100\,GeV, one year of public {\it Fermi} Large Area Telescope ({\it Fermi}-LAT) data are also analyzed to complement the MAGIC data. The extrapolation of the exponential cutoff spectrum determined with the Fermi-LAT data is inconsistent with MAGIC measurements, which requires a modification of the standard pulsar emission models. In the energy region between 25 and 100\,GeV, the emission in the P1 phase (from -0.06 to 0.04, location of the main pulse) and the P2 phase (from 0.32 to 0.43, location of the interpulse) can be described by power laws with spectral indices of $-3.1 \pm 1.0_{stat} \pm 0.3_{syst}$ and $-3.5 \pm 0.5_{stat} \pm 0.3_{syst}$, respectively. Assuming an asymmetric Lorentzian for the pulse shape, the peak positions of the main pulse and the interpulse are estimated to be at phases $-0.009 \pm 0.007$ and $0.393 \pm 0.009$, while the full widths at half maximum are $0.025 \pm 0.008$ and $0.053 \pm 0.015$, respectively.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122844eng(c) American Astronomical Society, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3263572020-02-14T14:28:10Zhdl_2072_169514The intricate Galaxy disk: velocity asymmetries in Gaia-TGASAntoja Castelltort, M. TeresaBruijne, J. deFigueras Siñol, FrancescaMor Crespo, RogerPrusti, T.Roca Fàbrega, SantiFormació de les galàxiesCinemàtica galàcticaGalaxy formationGalactic kinematicsWe use Gaia-TGAS data to compare the transverse velocities in Galactic longitude (coming from proper motions and parallaxes) in the Milky Way disk for negative and positive longitudes as a function of distance. The transverse velocities are strongly asymmetric and deviate significantly from the expectations for an axisymmetric galaxy. The value and sign of the asymmetry changes at spatial scales of several tens of degrees in Galactic longitude and about 0.5 kpc in distance. The asymmetry is statistically significant at 95% confidence level for 57% of the region probed, which extends up to 1.2 kpc. A percentage of 24% of the region shows absolute differences at this confidence level larger than 5 km s-1 and 7% larger than 10 km s-1. The asymmetry pattern shows mild variations in the vertical direction and with stellar type. A first qualitative comparison with spiral arm models indicates that the arms are probably not the main source of the asymmetry. We briefly discuss alternative origins. This is the first time that global all-sky asymmetries are detected in the Milky Way kinematics beyond the local neighbourhood and with a purely astrometric sample.EDP SciencesUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/122955eng(c) The European Southern Observatory (ESO), 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3265432020-02-14T14:28:11Zhdl_2072_169514The open cluster King 1 in the second quadrantCarrera, RicardoRodríguez Espinosa, LoretoCasamiquela Floriach, LaiaBalaguer Núñez, María de los DoloresJordi i Nebot, CarmeAllende Prieto, CarlosStetson, Peter B.Cúmuls d'estelsGalàxiesClusters of starsGalaxiesWe analyse the poorly studied open cluster King 1 in the second Galactic quadrant. From wide-field photometry, we have studied the spatial distribution of this cluster. We determined that the centre of King 1 is located at α2000 = 00h22m and δ2000 = +64°23΄. By parameterizing the stellar density with a King profile, we have obtained a central density of ρ0 = 6.5 ± 0.2 star arcmin-2 and a core radius of rcore = 1.9 ± 0.2 arcmin. By comparing the observed colour-magnitude diagram of King 1 with those of similar open clusters and with different sets of isochrones, we have estimated an age of 2.8 ± 0.3 Gyr, a distance modulus of (m - M)o = 10.6 ± 0.1 mag and a reddening of E(B - V) = 0.80 ± 0.05 mag. To complete our analysis, we acquired medium resolution spectra for 189 stars in the area of King 1. From their derived radial velocities, we determined an average velocity = -53.1 ± 3.1 km s-1. From the strength of the infrared Ca II lines in red giants we have determined an average metallicity of <[M/H]> = +0.07 ± 0.08 dex. From spectral synthesis, we have also estimated an α-elements abundance of <[α/M]> = -0.10 ± 0.08 dex.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123120eng(c) Carrera, Ricardo et al., 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2854892020-02-14T14:28:11Zhdl_2072_169514First observation of the decay B+→π+μ+μ−Abellan Beteta, CarlosCalvo Gómez, MíriamCamboni, AlessandroComerma Montells, AlbertDomingo Bonal, FrancescGarrido Beltrán, LluísGascón Fora, DavidGrabalosa Gándara, MarcGraciani Díaz, RicardoGraugés Pous, EugeniLópez Asamar, EliasPérez-Calero Yzquierdo, AntonioPicatoste Olloqui, EduardoPie Valls, B. (Blai)Potterat, CédricPuig Navarro, AlbertRoselló, M.Ruiz, Hugo (Ruiz Pérez)Vázquez Gómez, RicardVilasis-Cardona, XavierLHCb CollaborationTeoria quàntica de campsPartícules (Física nuclear)HadronsFísica nuclearDetectors de radiacióQuantum field theoryParticles (Nuclear physics)HadronsNuclear physicsNuclear countersA discovery of the rare decay B + → π + μ + μ − is presented. This decay is observed for the first time, with 5.2 σ significance. The observation is made using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected with the LHCb detector. The measured branching fraction is (2.3 ± 0.6 (stat.) ± 0.1 (syst.))×10−8, and the ratio of the B + → π + μ + μ − and B + → K + μ + μ − branching fractions is measured to be 0.053 ± 0.014 (stat.) ± 0.001 (syst.).Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/56475engcc by (c) LHCb Collaboration, 2012info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/">http://creativecommons.org/licenses/by/3.0/</a>
oai:recercat.cat:2072/3266222020-02-14T14:28:11Zhdl_2072_169514OCCASO - II. Physical parameters and Fe abundances of red clump stars in 18 open clustersCasamiquela Floriach, LaiaCarrera, R.Blanco Cuaresma, S.Jordi i Nebot, CarmeBalaguer Núñez, María de los DoloresPancino, E.Anders, F.Chiappini, C.Díaz Pérez, L.Aguado, D. S.Aparicio, A.García Dias, R.Heiter, U.Martínez Vázquez, C. E.Murabito, S.Pino, A. delEspectroscòpiaCúmuls de galàxiesSpectrum analysisClusters of galaxiesOpen clusters have long been used to study the chemodynamical evolution of the Galactic disc. This requires a homogeneously analysed sample covering a wide range of ages and distances. In this paper, we present the Open Clusters Chemical Abundances from Spanish Observatories (OCCASO) second data release. This comprises a sample of high-resolution (R > 65 000) and high signal-to-noise spectra of 115 red clump stars in 18 open clusters. We derive atmospheric parameters (Teff, log g, ξ), and [Fe/H] abundances using two analysis techniques: equivalent widths and spectral synthesis. A detailed comparison and a critical review of the results of the two methods are made. Both methods are carefully tested between them, with the Gaia FGK benchmark stars, and with an extensive sample of literature values. We perform a membership study using radial velocities and the resulting abundances. Finally, we compare our results with a chemodynamical model of the Milky Way thin disc concluding that the oldest open clusters are consistent with the models only when dynamical effects are taken into account.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123177eng(c) Casamiquela Floriach, Laia et al., 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3266232020-02-14T14:28:12Zhdl_2072_169514Search for very high-energy gamma-ray emission from the microquasar Cygnus X-1 with the MAGIC telescopesGalindo Fernández, DanielParedes i Poy, Josep MariaParedes Fortuny, XavierRibó Gomis, MarcTorres Albà, NúriaBosch i Ramon, ValentíMAGIC CollaborationRaigs gammaEstels binaris de raigs XForats negres (Astronomia)Gamma raysX-ray binariesBlack holes (Astronomy)The microquasar Cygnus X-1 displays the two typical soft and hard X-ray states of a black hole transient. During the latter, Cygnus X-1 shows a one-sided relativistic radio-jet. Recent detection of the system in the high energy (HE; E ≳ 60 MeV) gamma-ray range with Fermi-LAT associates this emission with the outflow. Former MAGIC observations revealed a hint of flaring activity in the very high-energy (VHE; E ≳ 100 GeV) regime during this X-ray state. We analyse ∼97 h of Cygnus X-1 data taken with the MAGIC telescopes between July 2007 and October 2014. To shed light on the correlation between hard X-ray and VHE gamma rays as previously suggested, we study each main X-ray state separately. We perform an orbital phase-folded analysis to look for variability in the VHE band. Additionally, to place this variability behaviour in a multiwavelength context, we compare our results with Fermi-LAT, AGILE, Swift-BAT, MAXI, RXTE-ASM, AMI and RATAN-600 data. We do not detect Cygnus X-1 in the VHE regime. We establish upper limits for each X-ray state, assuming a power-law distribution with photon index Γ = 3.2. For steady emission in the hard and soft X-ray states, we set integral upper limits at 95 per cent confidence level for energies above 200 GeV at 2.6 × 10−12 photons cm−2 s−1 and 1.0 × 10−11 photons cm−2 s−1, respectively. We rule out steady VHE gamma-ray emission above this energy range, at the level of the MAGIC sensitivity, originating in the interaction between the relativistic jet and the surrounding medium, while the emission above this flux level produced inside the binary still remains a valid possibility.Royal Astronomical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123183eng(c) Galindo, D. et al., 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3266242020-02-14T14:28:12Zhdl_2072_169514A galactic microquasar mimicking winged radio galaxiesMartí, JosepLuque Escamilla, Pedro L.Bosch i Ramon, ValentíParedes i Poy, Josep MariaQuàsarsGalàxiesQuasarsGalaxiesA subclass of extragalactic radio sources known as winged radio galaxies has puzzled astronomers for many years. The wing features are detected at radio wavelengths as low-surface-brightness radio lobes that are clearly misaligned with respect to the main lobe axis. Different models compete to account for these peculiar structures. Here, we report observational evidence that the parsec-scale radio jets in the Galactic microquasar GRS 1758-258 give rise to a Z-shaped radio emission strongly reminiscent of the X and Z-shaped morphologies found in winged radio galaxies. This is the first time that such extended emission features are observed in a microquasar, providing a new analogy for its extragalactic relatives. From our observations, we can clearly favour the hydrodynamic backflow interpretation against other possible wing formation scenarios. Assuming that physical processes are similar, we can extrapolate this conclusion and suggest that this mechanism could also be at work in many extragalactic cases.Nature Publishing GroupUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123185engcc-by (c) Martí, Josep et al., 2017info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3302502020-02-14T14:28:13Zhdl_2072_169514Loop effects of heavy new scalars and fermions in b → sμ + μ −Arnan, PereCrivellin, AndreasHofer, LarsMescia, FedericoQuarksPartícules (Física nuclear)QuarksParticles (Nuclear physics)Recent measurements of b → sμ + μ − processes at LHCb and BELLE have revealed tensions at the 2 − 3σ level between the Standard Model (SM) prediction and the experimental results in the channels B → K * μ + μ − and B s → ϕμ + μ −, as well as in the lepton-flavor universality violating observable R K = Br(B → Kμ + μ −)/Br(B → Ke + e −). Combined global fits to the available b → sμ + μ − data suggest that these tensions might have their common origin in New Physics (NP) beyond the SM because some NP scenarios turn out to be preferred over the SM by 4 − 5σ. The fact that all these anomalies are related to muons further suggests a connection (and a common NP explanation) with the long-standing anomaly in the anomalous magnetic moment of the muon, a μ . In this article, we study the impact of a generic class of NP models featuring new heavy scalars and fermions that couple to the SM fermions via Yukawa-like interactions. We consider two different scenarios, introducing either one additional fermion and two scalars or two additional fermions and one scalar, and examine all possible representations of the new particles under the SM gauge group with dimension up to the adjoint one. The models induce one-loop contributions to b → sμ + μ − and a μ which are capable of solving the respective anomalies at the 2σ level, albeit a relatively large coupling of the new particles to muons is required. In the case of b → sμ + μ −, stringent constraints from Bs−B¯¯¯¯s mixing arise which can be relaxed if the new fermion is a Majorana particle.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123336engcc-by (c) Arnan, Pere et al., 2017info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3302512020-02-14T14:28:13Zhdl_2072_169514Two Higgs doublet models and b→ s exclusive decaysArnan, PereBečirević, DamirMescia, FedericoSumensari, OlcyrSimetria (Física)BosonsSymmetry (Physics)BosonsWe computed the leading order Wilson coefficients relevant to all the exclusive b→sℓ+ℓ− decays in the framework of the two Higgs doublet model (2HDM) with a softly broken Z2 symmetry by including the O(mb) corrections. We elucidate the issue of appropriate matching between the full and the effective theory when dealing with the (pseudo-)scalar operators for which keeping the external momenta different from zero is necessary. We then make a phenomenological analysis by using the measured B(Bs→μ+μ−) and B(B→Kμ+μ−)high−q2 , for which the hadronic uncertainties are well controlled, and we discuss their impact on various types of 2HDM. A brief discussion of the decays with τ -leptons in the final state is provided too.Società Italiana di Fisica & Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123339engcc-by (c) Arnan, Pere et al., 2017info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3302522020-02-14T14:28:13Zhdl_2072_169514Window for preferred axion modelsDi Luzio, LucaMescia, FedericoNardi, EnricoPartícules (Matèria)ParticlesWe discuss phenomenological criteria for defining "axion windows," namely regions in the parameter space of the axion-photon coupling where realistic models live. Currently, the boundaries of this region depend on somewhat arbitrary criteria, and it would be highly desirable to specify them in terms of precise phenomenological requirements. We first focus on hadronic axion models within post-inflationary scenarios, in which the initial abundance of the new vectorlike quarks Q is thermal. We classify their representations R Q by requiring that (i) the Q are sufficiently short lived to avoid issues with long-lived strongly interacting relics, (ii) the theory remains weakly coupled up to the Planck scale. The more general case of multiple R Q is also studied, and the absolute upper and lower bounds on the axion-photon coupling as a function of the axion mass is identified. Pre-inflationary scenarios in which the axion decay constant remains bounded as f a ≤ 5 × 10 11 GeV allow for axion-photon couplings only about 20% larger. Realistic Dine-Fischler-Srednicki-Zhitnitsky type of axion models also remain encompassed within the hadronic axion window. Some mechanisms that can allow to enhance the axion-photon coupling to values sizeably above the preferred window are discussed.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123340eng(c) American Physical Society, 2017info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3307402020-02-14T14:28:14Zhdl_2072_169514Search for mixing-induced CP violation using partial reconstruction of B¯0→D*+Xℓ−ν¯ℓ and kaon taggingGraugés Pous, EugeniBABAR CollaborationPartícules (Matèria)Mesons (Física nuclear)Violació CP (Física nuclear)ParticlesMesons (Nuclear physics)CP violation (Nuclear physics)We describe in detail a previously published measurement of C P violation in B 0 - ¯ B 0 oscillations, based on an integrated luminosity of 425.7 fb − 1 collected by the BABAR experiment at the PEPII collider. We apply a novel technique to a sample of about 6 million ¯ B 0 → D * + ℓ − ¯ ν ℓ decays selected with partial reconstruction of the D * + meson. The charged lepton identifies the flavor of one B meson at its decay time, the flavor of the other B is determined by kaon tagging. We determine a C P violating asymmetry A C P = ( N ( B 0 B 0 ) − N ( ¯ B 0 ¯ B 0 ) ) / ( N ( B 0 B 0 ) + N ( ¯ B 0 ¯ B 0 ) ) = ( 0.06 ± 0.1 7 + 0.38 − 0.32 ) % corresponding to Δ C P = 1 − | q / p | = ( 0.29 ± 0.8 4 + 1.88 − 1.61 ) × 1 0 − 3 . This measurement is consistent and competitive with those obtained at the B factories with dilepton events.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123645eng(c) American Physical Society, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3307412020-02-14T14:28:14Zhdl_2072_169514Search for Structure in the Bs0 π± Invariant Mass SpectrumBadalov, AlexeyCamboni, AlessandroGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationHadronsCromodinàmica quànticaHadronsQuantum chromodynamicsThe B 0 s π ± invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to 3 fb − 1 of p p collision data at √ s = 7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X ( 5568 ) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B 0 s π ± final state. The same limits also apply to a possible exotic meson decaying through the chain B * 0 s π ± , B * 0 s → B 0 s γ where the photon is excluded from the reconstructed decays.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123649eng(c) American Physical Society, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3307422020-02-14T14:28:14Zhdl_2072_169514Studies of the resonance structure in D0 → KS0 K±π decaysGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséRuiz, Hugo (Ruiz Pérez)LHCb CollaborationHadronsMesons (Física nuclear)HadronsMesons (Nuclear physics)Amplitude models are applied to studies of resonance structure in D 0 → K 0 S K − π + and D 0 → K 0 S K + π − decays using p p collision data corresponding to an integrated luminosity of 3.0 fb − 1 collected by the LHCb experiment. Relative magnitude and phase information is determined, and coherence factors and related observables are computed for both the whole phase space and a restricted region of 100 MeV / c 2 around the K ∗ ( 892 ) ± resonance. Two formulations for the K π S -wave are used, both of which give a good description of the data. The ratio of branching fractions B ( D 0 → K 0 S K + π − ) / B ( D 0 → K 0 S K − π + ) is measured to be 0.655 ± 0.004 ( stat ) ± 0.006 ( syst ) over the full phase space and 0.370 ± 0.003 ( stat ) ± 0.012 ( syst ) in the restricted region. A search for C P violation is performed using the amplitude models and no significant effect is found. Predictions from SU(3) flavor symmetry for K ∗ ( 892 ) K amplitudes of different charges are compared with the amplitude model results.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123650eng(c) American Physical Society, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3307432020-02-14T14:28:14Zhdl_2072_169514Study of Bc+ decays to the K+K-π+ final state and evidence for the decay Bc+ →χc0π+Coquereau, S.Garrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationInteraccions d'hadronsMesons (Física nuclear)Hadron interactionsMesons (Nuclear physics)A study of B + c → K + K − π + decays is performed for the first time using data corresponding to an integrated luminosity of 3.0 fb − 1 collected by the LHCb experiment in p p collisions at center-of-mass energies of 7 and 8 TeV. Evidence for the decay B + c → χ c 0 ( → K + K − ) π + is reported with a significance of 4.0 standard deviations, giving σ ( B + c ) σ ( B + ) × B ( B + c → χ c 0 π + ) = ( 9. 8 + 3.4 − 3.0 ( stat ) ± 0.8 ( syst ) ) × 10 − 6 . Here B denotes a branching fraction while σ ( B + c ) and σ ( B + ) are the production cross sections for B + c and B + mesons. An indication of ¯ b c weak annihilation is found for the region m ( K − π + ) < 1.834 GeV / c 2 , with a significance of 2.4 standard deviations.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123651eng(c) American Physical Society, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2854902020-02-14T14:28:15Zhdl_2072_169514Opposite-side flavour tagging of B mesons at the LHCb experimentAbellan Beteta, CarlosCalvo Gómez, MíriamCamboni, AlessandroComerma Montells, AlbertDomingo Bonal, FrancescGarrido Beltrán, LluísGascón Fora, DavidGrabalosa Gándara, MarcGraciani Díaz, RicardoGraugés Pous, EugeniLópez Asamar, EliasMusy, MarcoPérez-Calero Yzquierdo, AntonioPicatoste Olloqui, EduardoPie Valls, B. (Blai)Potterat, CédricPuig Navarro, AlbertRoselló, M.Ruiz, Hugo (Ruiz Pérez)Vázquez Gómez, RicardVilasis-Cardona, XavierLHCb CollaborationFísica nuclearTeoria quàntica de campsHadronsMesons (Física nuclear)Gran Col·lisionador d'HadronsNuclear physicsQuantum field theoryHadronsMesons (Nuclear physics)Large Hadron Collider (France and Switzerland)The calibration and performance of the opposite-side flavour tagging algorithms used for the measurements of time-dependent asymmetries at the LHCb experiment are described. The algorithms have been developed using simulated events and optimized and calibrated with B +→J/ψK +, B 0→J/ψK ∗0 and B 0→D ∗− μ + ν μ decay modes with 0.37 fb−1 of data collected in pp collisions at s√=7~TeV during the 2011 physics run. The opposite-side tagging power is determined in the B +→J/ψK + channel to be (2.10±0.08±0.24) %, where the first uncertainty is statistical and the second is systematic.Società Italiana di Fisica & Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/57570engcc-by (c) LHCb Collaboration, 2012info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es/">http://creativecommons.org/licenses/by/3.0/es/</a>
oai:recercat.cat:2072/3307442020-02-14T14:28:15Zhdl_2072_169514Study of DsJ(*) + mesons decaying to D∗ +KS0 and D*0K+ final statesGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarín Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséLHCb CollaborationInteraccions d'hadronsFísica còsmicaHadron interactionsCosmic physicsA search is performed for D sJ (*) + mesons in the reactions pp → D ∗ + K S 0 X and pp → D *0 K + X using data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb detector. For the D ∗ + K S 0 final state, the decays D *+ → D 0 π + with D 0 → K − π + and D 0 → K − π + π + π − are used. For D *0 K +, the decay D *0 → D 0 π 0 with D 0 → K − π + is used. A prominent D s1(2536)+ signal is observed in both D ∗ + K S 0 and D *0 K + final states. The resonances D s1 * (2700)+ and D s3 * (2860)+ are also observed, yielding information on their properties, including spin-parity assignments. The decay D s2 * (2573)+ → D ∗ + K S 0 is observed for the first time, at a significance of 6.9 σ, and its branching fraction relative to the D s2 * (2573)+ → D + K S 0 decay mode is measured.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123652engcc-by (c) Gascón Fora, David et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3307452020-02-14T14:28:15Zhdl_2072_169514Tests of CPT symmetry in B0- B 0 mixing and in B0 →c c K0 decaysGraugés Pous, EugeniBABAR CollaborationSimetria (Física)HadronsPartícules (Matèria)Symmetry (Physics)HadronsParticlesUsing the eight time dependences e − Γ t ( 1 + C i cos Δ m t + S i sin Δ m t ) for the decays Υ ( 4 S ) → B 0 ¯ B 0 → f j f k , with the decay into a flavor-specific state f j = ℓ ± X before or after the decay into a C P eigenstate f k = c ¯ c K S , L , as measured by the BABAR experiment, we determine the three C P T -sensitive parameters Re ( z ) and Im ( z ) in B 0 − ¯ B 0 mixing and | ¯ A / A | in B 0 → c ¯ c K 0 decays. We find Im ( z ) = 0.010 ± 0.030 ± 0.013 , Re ( z ) = − 0.065 ± 0.028 ± 0.014 , and | ¯ A / A | = 0.999 ± 0.023 ± 0.017 , in agreement with C P T symmetry.American Physical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/123654eng(c) American Physical Society, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3340322020-02-14T14:28:16Zhdl_2072_169514PACIFIC: the readout ASIC for the SciFi Tracker of the upgraded LHCb detectorMazorra, JoséChanal, HerveComerma, AlbertGascón Fora, DavidGomez, SergioHan, X.Pillet, NicolasVandaele, R.LHCb CollaborationCircuits electrònicsDetectorsElectrònica digitalElectronic circuitsDetectorsDigital electronicsThe LHCb detector will be upgraded during the Long Shutdown 2 (LS2) of the LHC in order to cope with higher instantaneous luminosities and will switch to a 40 MHz readout rate using a trigger-less software based system. All front-end electronics will be replaced and several sub-detectors must be redesigned to cope with the higher detector occupancy and radiation damage. The current tracking detectors downstream of the LHCb dipole magnet will be replaced by the Scintillating Fibre (SciFi) Tracker. The SciFi Tracker will use scintillating fibres read out by Silicon Photomultipliers (SiPMs). State-of-the-art multi-channel SiPM arrays are being developed and a custom ASIC, called the low-Power ASIC for the sCIntillating FIbres traCker (PACIFIC), will be used to digitise the signals from the SiPMs. This article presents an overview of the R&D for the PACIFIC. It is a 64-channel ASIC implemented in 130 nm CMOS technology, aiming at a radiation tolerant design with a power consumption below 10 mW per channel. It interfaces directly with the SiPM anode through a current mode input, and provides a configurable non-linear 2-bit per channel digital output. The SiPM signal is acquired by a current conveyor and processed with a fast shaper and a gated integrator. The digitization is performed using a three threshold non-linear flash ADC operating at 40 MHz. Simulation and test results show the PACIFIC chip prototypes functioning well.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/125284engcc-by (c) Mazorra, José et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/3355472020-02-14T14:28:16Zhdl_2072_169514Gaia Data Release 1: Summary of the astrometric, photometric and survey propertiesMor Crespo, RogerRomero Gómez, MercèGonzález Vidal, Juan JoséPortell i de Mora, JordiJordi i Nebot, CarmeLuri Carrascoso, XavierMasana Fresno, EduardTorra Roca, JorgeBalaguer Núñez, María de los DoloresFabricius, ClausFigueras Siñol, FrancescaFries, AidanCastañeda Pons, Javier BernardoCarrasco Martínez, José ManuelGràcia Abril, G.Antiche Garzón, ErikaBorrachero, R.Clotet Altarriba, MarcialFarràs Casas, M.Garralda, N.Gúrpide Lasheras, AndrésSoria Nieto, SergioVoss, HölgerWeiler, MichaelAnglada Escudé, G.Gallardo, E.Isasi Parache, Y.Julbe, F.Molina Martínez, DanielGebran, M.Martínez Rubí, O.Palmer, MaxPeralta, J.Valles, P.Gaia CollaborationAstrometriaParal·laxiAstrometryParallaxContext. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion on the limitations due to the preliminary nature of this release. Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues - a realisation of the Tycho-Gaia Astrometric Solution (TGAS) - and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼ 3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr−1for the proper motions. To the parallax uncertainties a systematic component of ∼ 0.3 mas should be added. For the subset of ∼ 94 000 Hipparcos stars in the primary data set the proper motions are much more precise, at about 0.06 mas yr−1 . For the secondary astrometric data set the typical uncertainty of the positions is ∼ 10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼ 0.03 mag over the magnitude range 5 to 20.7. Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature 5-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data.EDP SciencesUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/125903eng(c) The European Southern Observatory (ESO), 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3372742020-02-14T14:28:16Zhdl_2072_169514Perturbation theory approach for the power spectrum: from dark matter in real space to haloes in redshift spaceGil Marín, HéctorWagner, ChristianVerde, LiciaPorciani, CristianoJiménez, Raúl (Jiménez Tellado)CosmologiaMatèria interstel·larCosmologyInterstellar matterWe investigate the accuracy of Eulerian perturbation theory for describing the matter and galaxy power spectra in real and redshift space in light of future observational probes for precision cosmology. Comparing the analytical results with a large suite of N-body simulations (160 independent boxes of 13.8 (Gpc/h)3 volume each, which are publicly available), we find that re-summing terms in the standard perturbative approach predicts the real-space matter power spectrum with an accuracy of lesssim2% for k ≤ 0.20 h/Mpc at redshifts zlesssim1.5. This is obtained following the widespread technique of writing the resummed propagator in terms of 1-loop contributions. We show that the accuracy of this scheme increases by considering higher-order terms in the resummed propagator. By combining resummed perturbation theories with several models for the mappings from real to redshift space discussed in the literature, the multipoles of the dark-matter power spectrum can be described with sub-percent deviations from N-body results for k ≤ 0.15 h/Mpc at zlesssim1. As a consequence, the logarithmic growth rate, f, can be recovered with sub-percent accuracy on these scales. Extending the models to massive dark-matter haloes in redshift space, our results describe the monopole term from N-body data within 2% accuracy for scales k ≤ 0.15 h/Mpc at zlesssim0.5; here f can be recovered within < 5% when the halo bias is known. We conclude that these techniques are suitable to extract cosmological information from future galaxy surveys.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/126624engcc by (c) Gil Marín, Héctor et al., 2012info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es/">http://creativecommons.org/licenses/by/3.0/es/</a>
oai:recercat.cat:2072/3372752020-02-14T14:28:17Zhdl_2072_169514Isocurvature modes and Baryon Acoustic Oscillations II: gains from combining CMB and Large Scale StructureCarbone, CarmelitaMangilli, AnnaVerde, LiciaCosmologiaBarionsAcústicaCosmologyBaryonsAcousticsWe consider cosmological parameters estimation in the presence of a non-zero isocurvature contribution in the primordial perturbations. A previous analysis showed that even a tiny amount of isocurvature perturbation, if not accounted for, could affect standard rulers calibration from Cosmic Microwave Background observations such as those provided by the Planck mission, affect Baryon Acoustic Oscillations interpretation, and introduce biases in the recovered dark energy properties that are larger than forecasted statistical errors from future surveys. Extending on this work, here we adopt a general fiducial cosmology which includes a varying dark energy equation of state parameter and curvature. Beside Baryon Acoustic Oscillations measurements, we include the information from the shape of the galaxy power spectrum and consider a joint analysis of a Planck-like Cosmic Microwave Background probe and a future, space-based, Large Scale Structure probe not too dissimilar from recently proposed surveys. We find that this allows one to break the degeneracies that affect the Cosmic Microwave Background and Baryon Acoustic Oscillations combination. As a result, most of the cosmological parameter systematic biases arising from an incorrect assumption on the isocurvature fraction parameter fiso, become negligible with respect to the statistical errors. We find that the Cosmic Microwave Background and Large Scale Structure combination gives a statistical error σ(fiso) ~ 0.008, even when curvature and a varying dark energy equation of state are included, which is smaller that the error obtained from Cosmic Microwave Background alone when flatness and cosmological constant are assumed. These results confirm the synergy and complementarity between Cosmic Microwave Background and Large Scale Structure, and the great potential of future and planned galaxy surveys.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/126625eng(c) IOP Publishing and Sissa Medialab, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/3464322020-02-14T14:28:17Zhdl_2072_169514Constraints on cosmic opacity and beyond the standard model physics from cosmological distance measurementsAvgoustidis, AnastasiosBurrage, ClareRedondo, JavierVerde, LiciaJiménez, Raúl (Jiménez Tellado)CosmologiaSupernovesEnergia fosca (Astronomia)CosmologySupernovaeDark energy (Astronomy)We update constraints on cosmic opacity by combining recent SN Type Ia data with the latest measurements of the Hubble expansion at redshifts between 0 and 2. The new constraint on the parameter epsilon parametrising deviations from the luminosity-angular diameter distance relation (dL = dA(1+z)2+epsilon), is epsilon = −0.04−0.07+0.08 (2-σ). For the redshift range between 0.2 and 0.35 this corresponds to an opacity Δτ < 0.012 (95% C.L.), a factor of 2 stronger than the previous constraint. Various models of beyond the standard model physics that predict violation of photon number conservation contribute to the opacity and can be equally constrained. In this paper we put new limits on axion-like particles, including chameleons, and mini-charged particles.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/127508engcc by (c) Avgoustidis, Anastasios et al., 2010info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es/">http://creativecommons.org/licenses/by/3.0/es/</a>
oai:recercat.cat:2072/3464372020-02-14T14:28:17Zhdl_2072_169514The effective Lagrangian of dark energy from observationsJiménez, Raúl (Jiménez Tellado)Talavera, PereVerde, LiciaMoresco, MicheleCimatti, AndreaPozzeti, LuciaFenomenologiaEnergia fosca (Astronomia)CosmologiaPhenomenologyDark energy (Astronomy)CosmologyUsing observational data on the expansion rate of the universe (H(z)) we constrain the effective Lagrangian of the current accelerated expansion. Our results show that the effective potential is consistent with being flat i.e., a cosmological constant; it is also consistent with the field moving along an almost flat potential like a pseudo-Goldstone boson. We show that the potential of dark energy does not deviate from a constant at more than 6% over the redshift range 0 < z < 1. The data can be described by just a constant term in the Lagrangian and do not require any extra parameters; therefore there is no evidence for augmenting the number of parameters of the LCDM paradigm. We also find that the data justify the effective theory approach to describe accelerated expansion and that the allowed parameters range satisfy the expected hierarchy. Future data, both from cosmic chronometers and baryonic acoustic oscillations, that can measure H(z) at the % level, could greatly improve constraints on the flatness of the potential or shed some light on possible mechanisms driving the accelerated expansion. Besides the above result, it is shown that the effective Lagrangian of accelerated expansion can be constrained from cosmological observations in a model-independent way and that direct measurements of the expansion rate H(z) are most useful to do so.Institute of Physics (IOP)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/127509eng(c) IOP Publishing and Sissa Medialab, 2012info:eu-repo/semantics/openAccess
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