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Öğe Measurement of b-quark fragmentation properties in jets using the decay B ± ? J/?K ± in pp collisions at ?s = 13 TeV with the ATLAS detector(Springer Science and Business Media Deutschland GmbH, 2021) Aad, G.; Abbott, B.; Abbott, D.C.; Abed Abud, A.; Abeling, K.The fragmentation properties of jets containing b-hadrons are studied using charged B mesons in 139 fb?1 of pp collisions at s = 13 TeV, recorded with the ATLAS detector at the LHC during the period from 2015 to 2018. The B mesons are reconstructed using the decay of B± into J/?K±, with the J/? decaying into a pair of muons. Jets are reconstructed using the anti-kt algorithm with radius parameter R = 0.4. The measurement determines the longitudinal and transverse momentum profiles of the reconstructed B hadrons with respect to the axes of the jets to which they are geometrically associated. These distributions are measured in intervals of the jet transverse momentum, ranging from 50 GeV to above 100 GeV. The results are corrected for detector effects and compared with several Monte Carlo predictions using different parton shower and hadronisation models. The results for the longitudinal and transverse profiles provide useful inputs to improve the description of heavy-flavour fragmentation in jets. [Figure not available: see fulltext.]. © 2021, The Author(s).Öğe Search for heavy particles in the b -tagged dijet mass distribution with additional b -tagged jets in proton-proton collisions at s =13 TeV with the ATLAS experiment(American Physical Society, 2022) Aad, G.; Abbott, B.; Abbott, D.C.; Abed Abud, A.; Abeling, K.; Abhayasinghe, D.K.; Çetin, Serkant AliA search optimized for new heavy particles decaying to two b-quarks and produced in association with additional b-quarks is reported. The sensitivity is improved by b-tagging at least one lower-pT jet in addition to the two highest-pT jets. The data used in this search correspond to an integrated luminosity of 103 fb-1 collected with a dedicated trijet trigger during the 2017 and 2018 s=13 TeV proton-proton collision runs with the ATLAS detector at the LHC. The search looks for resonant peaks in the b-tagged dijet invariant mass spectrum over a smoothly falling background. The background is estimated with an innovative data-driven method based on orthonormal functions. The observed b-tagged dijet invariant mass spectrum is compatible with the background-only hypothesis. Upper limits at 95% confidence level on a heavy vector-boson production cross section times branching ratio to a pair of b-quarks are derived. © 2022 CERN.Öğe Search for Higgs boson decays into a pair of pseudoscalar particles in the bb?? final state with the ATLAS detector in pp collisions at s =13 TeV(American Physical Society, 2022) Aad, G.; Abbott, B.; Abbott, D.C.; Abed Abud, A.; Abeling, K.; Çetin, Serkant AliThis paper presents a search for decays of the Higgs boson with a mass of 125 GeV into a pair of new pseudoscalar particles, H?aa, where one a-boson decays into a b-quark pair and the other into a muon pair. The search uses 139 fb-1 of proton-proton collision data at a center-of-mass energy of s=13 TeV recorded between 2015 and 2018 by the ATLAS experiment at the LHC. A narrow dimuon resonance is searched for in the invariant mass spectrum between 16 GeV and 62 GeV. The largest excess of events above the Standard Model backgrounds is observed at a dimuon invariant mass of 52 GeV and corresponds to a local (global) significance of 3.3? (1.7?). Upper limits at 95% confidence level are placed on the branching ratio of the Higgs boson to the bb?? final state, B(H?aa?bb??), and are in the range 0.2-4.0×10-4, depending on the signal mass hypothesis. © 2022 CERN.