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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., Castillo, F. L., et al. (2021). Measurements of W+W-+ >= 1 jet production cross-sections in pp collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 06(6), 003–59pp.
Abstract: Fiducial and differential cross-section measurements of W+W- production in association with at least one hadronic jet are presented. These measurements are sensitive to the properties of electroweak-boson self-interactions and provide a test of perturbative quantum chromodynamics and the electroweak theory. The analysis is performed using proton-proton collision data collected at root s = 13TeV with the ATLAS experiment, corresponding to an integrated luminosity of 139 fb(-1). Events are selected with exactly one oppositely charged electron-muon pair and at least one hadronic jet with a transverse momentum of p(T) > 30 GeV and a pseudorapidity of vertical bar eta vertical bar < 4.5. After subtracting the background contributions and correcting for detector effects, the jet-inclusive W+W-+ >= 1 jet fiducial cross-section and W+W-+ jets differential cross-sections with respect to several kinematic variables are measured. These measurements include leptonic quantities, such as the lepton transverse momenta and the transverse mass of the W+W- system, as well as jet-related observables such as the leading jet transverse momentum and the jet multiplicity. Limits on anomalous triple-gauge-boson couplings are obtained in a phase space where interference between the Standard Model amplitude and the anomalous amplitude is enhanced.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2021). Measurement of the relative B-c(+/-)/B-+/- production cross section with the ATLAS detector at root s=8 TeV. Phys. Rev. D, 104(1), 012010–26pp.
Abstract: The total cross section and differential cross sections for the production of B-c(+/-) mesons, times their branching fraction to J/psi pi(+/-), are measured relative to those for the production of B-+/- mesons, times their branching fraction to J/psi K-+/-. The data used for this study correspond to an integrated luminosity of 20.3 fb(-1) of pp collisions recorded by the ATLAS detector at the Large Hadron Collider in 2012 at a center-of-mass energy of root s = 8 TeV. The measurement is performed differentially in bins of transverse momentum p(T) for 13 GeV < p(T)(B-c(+/-)) < 22 GeV and p(T)(B-c(+/-)) > 22 GeV and in bins of rapidity y for vertical bar y vertical bar < 0.75 and 0.75 < vertical bar y vertical bar < 2.3. The relative cross section times branching fraction for the full range p(T) > 13 GeV and vertical bar y vertical bar < 2.3 is (0.34 +/- 0.04(stat) (+0.06)(-0.02 sys) +/- 0.01(lifetime))%. The differential measurements suggest that the production cross section of the B-c(+/-) decreases faster with p(T) than the production cross section of the B-+/-, while no significant dependence on rapidity is observed.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., Castillo, F. L., et al. (2021). Measurements of Higgs bosons decaying to bottom quarks from vvector boson fusion production with the ATLAS experiment at root s=13 TeV. Eur. Phys. J. C, 81(6), 537–32pp.
Abstract: The paper presents a measurement of the Standard Model Higgs Boson decaying to b-quark pairs in the vector boson fusion (VBF) production mode. A sample corresponding to 126 fb(-1) of root s = 13 TeVproton-proton collision data, collected with the ATLAS experiment at the Large Hadron Collider, is analyzed utilizing an adversarial neural network for event classification. The signal strength, defined as the ratio of the measured signal yield to that predicted by the Standard Model for VBF Higgs production, is measured to be 0.95(-0.36)(+0.38), corresponding to an observed (expected) significance of 2.6 (2.8) standard deviations from the background only hypothesis. The results are additionally combined with an analysis of Higgs bosons decaying to b-quarks, produced via VBF in association with a photon.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., Castillo, F. L., et al. (2021). Muon reconstruction and identification efficiency in ATLAS using the full Run 2 pp collision data set at root s = 13 TeV. Eur. Phys. J. C, 81(7), 578–44pp.
Abstract: This article documents the muon reconstruction and identification efficiency obtained by the ATLAS experiment for 139 fb-1 of pp collision data at <mml:msqrt>s</mml:msqrt>=13 TeV collected between 2015 and 2018 during Run 2 of the LHC. The increased instantaneous luminosity delivered by the LHC over this period required a reoptimisation of the criteria for the identification of prompt muons. Improved and newly developed algorithms were deployed to preserve high muon identification efficiency with a low misidentification rate and good momentum resolution. The availability of large samples of Z -> μμand J/psi -> μμdecays, and the minimisation of systematic uncertainties, allows the efficiencies of criteria for muon identification, primary vertex association, and isolation to be measured with an accuracy at the per-mille level in the bulk of the phase space, and up to the percent level in complex kinematic configurations. Excellent performance is achieved over a range of transverse momenta from 3 GeV to several hundred GeV, and across the full muon detector acceptance of |eta|<2.7.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., Castillo, F. L., et al. (2021). Determination of the parton distribution functions of the proton from ATLAS measurements of differential W-+/- and Z boson production in association with jets. J. High Energy Phys., 07(7), 223–44pp.
Abstract: This article presents a new set of proton parton distribution functions, AT-LASepWZVjet20, produced in an analysis at next-to-next-to-leading order in QCD. The new data sets considered are the measurements of W+ and W- boson and Z boson production in association with jets in pp collisions at root s = 8 TeV performed by the ATLAS experiment at the LHC with integrated luminosities of 20.2 fb(-1) and 19.9 fb(-1), respectively. The analysis also considers the ATLAS measurements of differential W-+/- and Z boson production at root s = 7 TeV with an integrated luminosity of 4.6 fb(-1) and deep-inelastic-scattering data from e(+/-) p collisions at the HERA accelerator. An improved determination of the sea-quark densities at high Bjorken x is shown, while confirming a strange-quark density similar in size to the up- and down-sea-quark densities in the range x less than or similar to 0.02 found by previous ATLAS analyses.
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