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Öğe Charged-hadron production in pp, p+Pb, Pb+Pb, and Xe+Xe collisions at ?sNN = 5 TeV with the ATLAS detector at the LHC(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliThis paper presents measurements of charged-hadron spectra obtained in pp, p+Pb, and Pb+Pb collisions at s or sNN = 5.02 TeV, and in Xe+Xe collisions at sNN = 5.44 TeV. The data recorded by the ATLAS detector at the LHC have total integrated luminosities of 25 pb?1, 28 nb?1, 0.50 nb?1, and 3 ?b?1, respectively. The nuclear modification factors RpPb and R AA are obtained by comparing the spectra in heavy-ion and pp collisions in a wide range of charged-particle transverse momenta and pseudorapidity. The nuclear modification factor RpPb shows a moderate enhancement above unity with a maximum at p T ? 3 GeV; the enhancement is stronger in the Pb-going direction. The nuclear modification factors in both Pb+Pb and Xe+Xe collisions feature a significant, centrality-dependent suppression. They show a similar distinct p T-dependence with a local maximum at p T ? 2 GeV and a local minimum at p T ? 7 GeV. This dependence is more distinguishable in more central collisions. No significant |?|-dependence is found. A comprehensive comparison with several theoretical predictions is also provided. They typically describe R AA better in central collisions and in the p T range from about 10 to 100 GeV. [Figure not available: see fulltext.] © 2023, The Author(s).Öğe Combination of searches for invisible decays of the Higgs boson using 139 fb?1 of proton-proton collision data at s=13 TeV collected with the ATLAS experiment(Elsevier B.V., 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliMany extensions of the Standard Model predict the production of dark matter particles at the LHC. Sufficiently light dark matter particles may be produced in decays of the Higgs boson that would appear invisible to the detector. This Letter presents a statistical combination of searches for H?invisible decays where multiple production modes of the Standard Model Higgs boson are considered. These searches are performed with the ATLAS detector using 139 fb?1 of proton–proton collisions at a centre–of–mass energy of [Formula presented] at the LHC. In combination with the results at [Formula presented] and [Formula presented], an upper limit on the H?invisible branching ratio of 0.107 (0.077) at the 95% confidence level is observed (expected). These results are also interpreted in the context of models where the 125 GeV Higgs boson acts as a portal to dark matter, and limits are set on the scattering cross-section of weakly interacting massive particles and nucleons. © 2023 The Author(s)Öğe Determination of the strong coupling constant from transverse energy-energy correlations in multijet events at ?s = 13 TeV with the ATLAS detector(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliMeasurements of transverse energy-energy correlations and their associated azimuthal asymmetries in multijet events are presented. The analysis is performed using a data sample corresponding to 139 fb?1 of proton-proton collisions at a centre-of-mass energy of s = 13 TeV, collected with the ATLAS detector at the Large Hadron Collider. The measurements are presented in bins of the scalar sum of the transverse momenta of the two leading jets and unfolded to particle level. They are then compared to next-to-next-to-leading-order perturbative QCD calculations for the first time, which feature a significant reduction in the theoretical uncertainties estimated using variations of the renormalisation and factorisation scales. The agreement between data and theory is good, thus providing a precision test of QCD at large momentum transfers Q. The strong coupling constant ?s is extracted as a function of Q, showing a good agreement with the renormalisation group equation and with previous analyses. A simultaneous fit to all transverse energy-energy correlation distributions across different kinematic regions yields a value of ?s(mZ)=0.1175±0.0006(exp.)?0.0017+0.0034(theo.) , while the global fit to the asymmetry distributions yields ?s(mZ)=0.1185±0.0009(exp.)?0.0012+0.0025(theo.) . [Figure not available: see fulltext.]. © 2023, The Author(s).Öğe Evidence of off-shell Higgs boson production from ZZ leptonic decay channels and constraints on its total width with the ATLAS detector(Elsevier, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S. H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliThis Letter reports on a search for off-shell production of the Higgs boson using 139 fb(-1) of pp collision data at root s = 13 TeV collected by the ATLAS detector at the Large Hadron Collider. The signature is a pair of Z bosons, with contributions from both the production and subsequent decay of a virtual Higgs boson and the interference of that process with other processes. The two observable final states are ZZ -> 4l and Z Z -> 2l2 nu with l = e or mu. In the ZZ -> 4l final state, a dense Neural Network is used to enhance analysis sensitivity with respect to matrix element-based discrimination. The background-only hypothesis is rejected with an observed (expected) significance of 3.3 (2.2) standard deviations, representing experimental evidence for off-shell Higgs boson production. Assuming that no new particles enter the production of the virtual Higgs boson, its total width can be deduced from the measurement of its off-shell production cross-section. The measured total width of the Higgs boson is 4.5(-2.5)(+3.3) MeV, and the observed (expected) upper limit on the total width is found to be 10.5 (10.9) MeV at 95% confidence level. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Öğe Inclusive-photon production and its dependence on photon isolation in pp collisions at ?s = 13 TeV using 139 fb?1 of ATLAS data(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliMeasurements of differential cross sections are presented for inclusive isolated-photon production in pp collisions at a centre-of-mass energy of 13 TeV provided by the LHC and using 139 fb?1 of data recorded by the ATLAS experiment. The cross sections are measured as functions of the photon transverse energy in different regions of photon pseudorapidity. The photons are required to be isolated by means of a fixed-cone method with two different cone radii. The dependence of the inclusive-photon production on the photon isolation is investigated by measuring the fiducial cross sections as functions of the isolation-cone radius and the ratios of the differential cross sections with different radii in different regions of photon pseudorapidity. The results presented in this paper constitute an improvement with respect to those published by ATLAS earlier: the measurements are provided for different isolation radii and with a more granular segmentation in photon pseudorapidity that can be exploited in improving the determination of the proton parton distribution functions. These improvements provide a more in-depth test of the theoretical predictions. Next-to-leading-order QCD predictions from JETPHOX and SHERPA and next-to-next-to-leading-order QCD predictions from NNLOJET are compared to the measurements, using several parameterisations of the proton parton distribution functions. The measured cross sections are well described by the fixed-order QCD predictions within the experimental and theoretical uncertainties in most of the investigated phase-space region. [Figure not available: see fulltext.] © 2023, The Author(s).Öğe Luminosity determination in pp collisions at ?s=13 TeV using the ATLAS detector at the LHC(Institute for Ionics, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliThe luminosity determination for the ATLAS detector at the LHC during Run 2 is presented, with pp collisions at a centre-of-mass energy s=13 TeV. The absolute luminosity scale is determined using van der Meer beam separation scans during dedicated running periods in each year, and extrapolated to the physics data-taking regime using complementary measurements from several luminosity-sensitive detectors. The total uncertainties in the integrated luminosity for each individual year of data-taking range from 0.9% to 1.1%, and are partially correlated between years. After standard data-quality selections, the full Run 2 pp data sample corresponds to an integrated luminosity of 140.1 ± 1.2 fb - 1 , i.e. an uncertainty of 0.83%. A dedicated sample of low-pileup data recorded in 2017–2018 for precision Standard Model physics measurements is analysed separately, and has an integrated luminosity of 338.1 ± 3.1 pb - 1 . © 2023, The Author(s).Öğe Measurements of differential cross sections of Higgs boson production through gluon fusion in the H? WW*? e??? final state at ?s=13 TeV with the ATLAS detector(Springer Nature, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliHiggs boson production via gluon–gluon fusion is measured in the WW*? e?µ? decay channel. The dataset utilized corresponds to an integrated luminosity of 139 fb - 1 collected by the ATLAS detector from s=13 TeV proton–proton collisions delivered by the Large Hadron Collider between 2015 and 2018. Differential cross sections are measured in a fiducial phase space restricted to the production of at most one additional jet. The results are consistent with Standard Model expectations, derived using different Monte Carlo generators. © 2023, The Author(s).Öğe Model-independent search for the presence of new physics in events including H ? ?? with ?s = 13 TeV pp data recorded by the ATLAS detector at the LHC(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliA model-independent search for new physics leading to final states containing a Higgs boson, with a mass of 125.09 GeV, decaying to a pair of photons is performed with 139 fb?1 of s = 13 TeV pp collision data recorded by the ATLAS detector at the Large Hadron Collider at CERN. This search examines 22 final states categorized by the objects that are produced in association with the Higgs boson. These objects include isolated electrons or muons, hadronically decaying ?-leptons, additional photons, missing transverse momentum, and hadronic jets, as well as jets that are tagged as containing a b-hadron. No significant excesses above Standard Model expectations are observed and limits on the production cross section at 95% confidence level are set. Detector efficiencies are reported for all 22 signal regions, which can be used to convert detector-level cross-section limits reported in this paper to particle-level cross-section constraints. [Figure not available: see fulltext.]. © 2023, The Author(s).Öğe Search for exclusive Higgs and Z boson decays to ?? and Higgs boson decays to K*? with the ATLAS detector(Elsevier, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S. H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliSearches for the exclusive decays of the Higgs boson to an omega meson and a photon or a K* meson and a photon can probe flavour-conserving and flavour-violating Higgs boson couplings to light quarks, respectively. Searches for these decays, along with the analogous Z boson decay to an omega meson and a photon, are performed with a pp collision data sample corresponding to integrated luminosities of up to 134 fb(-1) collected at root s = 13 TeV with the ATLAS detector at the CERN Large Hadron Collider. The obtained 95% confidence-level upper limits on the respective branching fractions are B(H -> omega gamma) < 5.5 x 10(-4), B(H -> K*gamma) < 2.2 x 10(-4) and B(Z -> omega gamma) < 3.9 x 10(-6). The limits for H -> omega gamma and Z -> omega gamma) are 370 times and 140 times the Standard Model expected values, respectively. The result for Z -> omega gamma corresponds to a two-orders-of-magnitude improvement over the limit obtained by the DELPHI experiment at LEP.Öğe Search for exotic decays of the Higgs boson into long-lived particles in pp collisions at root s=13 TeV using displaced vertices in the ATLAS inner detector(SPRINGER, 2021) Aad, G.; Abbott, B.; Abbott, D. C.; Abud, A. Abed; Abeling, K.; Abhayasinghe, D. K.; Abidi, S. H.; Abramowicz, H.A novel search for exotic decays of the Higgs boson into pairs of long-lived neutral particles, each decaying into a bottom quark pair, is performed using 139 fb(-1)of root s = 13 TeV proton-proton collision data collected with the ATLAS detector at the LHC. Events consistent with the production of a Higgs boson in association with a leptonically decaying Z boson are analysed. Long-lived particle (LLP) decays are reconstructed from inner-detector tracks as displaced vertices with high mass and track multiplicity relative to Standard Model processes. The analysis selection requires the presence of at least two displaced vertices, effectively suppressing Standard Model backgrounds. The residual background contribution is estimated using a data-driven technique. No excess over Standard Model predictions is observed, and upper limits are set on the branching ratio of the Higgs boson to LLPs. Branching ratios above 10% are excluded at 95% confidence level for LLP mean proper lifetimes c tau as small as 4 mm and as large as 100 mm. For LLP masses below 40 GeV, these results represent the most stringent constraint in this lifetime regime.Öğe Search for neutral long-lived particles in pp collisions at ?s = 13 TeV that decay into displaced hadronic jets in the ATLAS calorimeter(Springer, 2022) Çetin, Serkant Ali; Beddall, Andrew John; Celebi, E.; Aad, G; Abbott, D.C.; Aboulhorma, A.; Abramowicz, H.; Abreu, H.; Bella, G.; Beloborodov, K.; Beretta, M.; Chan, W.S.; Chen, C.; Kolcu, Onur BuğraA search for decays of pair-produced neutral long-lived particles (LLPs) is presented using 139 fb?1 of proton-proton collision data collected by the ATLAS detector at the LHC in 2015–2018 at a centre-of-mass energy of 13 TeV. Dedicated techniques were developed for the reconstruction of displaced jets produced by LLPs decaying hadronically in the ATLAS hadronic calorimeter. Two search regions are defined for different LLP kinematic regimes. The observed numbers of events are consistent with the expected background, and limits for several benchmark signals are determined. For a SM Higgs boson with a mass of 125 GeV, branching ratios above 10% are excluded at 95% confidence level for values of c times LLP mean proper lifetime in the range between 20 mm and 10 m depending on the model. Upper limits are also set on the cross-section times branching ratio for scalars with a mass of 60 GeV and for masses between 200 GeV and 1 TeV. [Figure not available: see fulltext.] © 2022, The Author(s).Öğe Search for pair production of third-generation leptoquarks decaying into a bottom quark and a ? -lepton with the ATLAS detector(Institute for Ionics, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliA search for pair-produced scalar or vector leptoquarks decaying into a b-quark and a ? -lepton is presented using the full LHC Run 2 (2015–2018) data sample of 139 fb - 1 collected with the ATLAS detector in proton–proton collisions at a centre-of-mass energy of s=13 TeV. Events in which at least one ? -lepton decays hadronically are considered, and multivariate discriminants are used to extract the signals. No significant deviations from the Standard Model expectation are observed and 95% confidence-level upper limits on the production cross-section are derived as a function of leptoquark mass and branching ratio B into a ? -lepton and b-quark. For scalar leptoquarks, masses below 1460 GeV are excluded assuming B= 100 %, while for vector leptoquarks the corresponding limit is 1650 GeV (1910 GeV) in the minimal-coupling (Yang–Mills) scenario. © 2023, The Author(s).Öğe Search for single production of vector-like T quarks decaying into Ht or Zt in pp collisions at ?s=13 TeV with the ATLAS detector(Springer, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S. H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliThis paper describes a search for the single production of an up-type vector-like quark (T) decaying as T -> Ht or T -> Zt. The search utilises a dataset of pp collisions at root s = 13 TeV collected with the ATLAS detector during the 2015-2018 data-taking period of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb(-1). Data are analysed in final states containing a single lepton with multiple jets and b-jets. The presence of boosted heavy resonances in the event is exploited to discriminate the signal from the Standard Model background. No significant excess above the Standard Model expectation is observed, and 95% CL upper limits are set on the production cross section of T quarks in different decay channels. The results are interpreted in several benchmark scenarios to set limits on the mass and universal coupling strength (kappa) of the vector-like quark. For singlet T quarks, kappa values above 0.53 are excluded for all masses below 2.3 TeV. At a mass of 1.6 TeV, kappa values as low as 0.35 are excluded. For T quarks in the doublet scenario, where the production cross section is much lower, kappa values above 0.72 are excluded for all masses below 1.7 TeV, and this exclusion is extended to kappa above 0.55 for low masses around 1.0 TeV.Öğe Studies of the muon momentum calibration and performance of the ATLAS detector with pp collisions at ?s=13 TeV(Institute for Ionics, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant AliThis paper presents the muon momentum calibration and performance studies for the ATLAS detector based on the pp collisions data sample produced at s = 13 TeV at the LHC during Run 2 and corresponding to an integrated luminosity of 139 fb - 1 . An innovative approach is used to correct for potential charge-dependent momentum biases related to the knowledge of the detector geometry, using the Z? ?+?- resonance. The muon momentum scale and resolution are measured using samples of J/ ?? ?+?- and Z? ?+?- events. A calibration procedure is defined and applied to simulated data to match the performance measured in real data. The calibration is validated using an independent sample of ? ? ?+?- events. At the Z (J/ ?) peak, the momentum scale is measured with an uncertainty at the 0.05% (0.1%) level, and the resolution is measured with an uncertainty at the 1.5% (2%) level. The charge-dependent bias is removed with a dedicated in situ correction for momenta up to 450 GeV with a precision better than 0.03 TeV - 1 . © 2023, The Author(s).
