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Öğe Author Correction: A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery (Nature, (2022), 607, 7917, (52-59), 10.1038/s41586-022-04893-w)(Nature Research, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliCorrection to: Nature Published online 4 July 2022 In the version of this article initially published, the ATLAS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the article. © 2023, The Author(s).Öğe A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery(Nature Research, 2022) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliThe standard model of particle physics1–4 describes the known fundamental particles and forces that make up our Universe, with the exception of gravity. One of the central features of the standard model is a field that permeates all of space and interacts with fundamental particles5–9. The quantum excitation of this field, known as the Higgs field, manifests itself as the Higgs boson, the only fundamental particle with no spin. In 2012, a particle with properties consistent with the Higgs boson of the standard model was observed by the ATLAS and CMS experiments at the Large Hadron Collider at CERN10,11. Since then, more than 30 times as many Higgs bosons have been recorded by the ATLAS experiment, enabling much more precise measurements and new tests of the theory. Here, on the basis of this larger dataset, we combine an unprecedented number of production and decay processes of the Higgs boson to scrutinize its interactions with elementary particles. Interactions with gluons, photons, and W and Z bosons—the carriers of the strong, electromagnetic and weak forces—are studied in detail. Interactions with three third-generation matter particles (bottom (b) and top (t) quarks, and tau leptons (?)) are well measured and indications of interactions with a second-generation particle (muons, ?) are emerging. These tests reveal that the Higgs boson discovered ten years ago is remarkably consistent with the predictions of the theory and provide stringent constraints on many models of new phenomena beyond the standard model. © 2022, The Author(s).Öğe Inclusive and differential cross-sections for dilepton tt¯ production measured in ?s = 13 TeV pp collisions with the ATLAS detector(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliDifferential and double-differential distributions of kinematic variables of leptons from decays of top-quark pairs (tt¯) are measured using the full LHC Run 2 data sample collected with the ATLAS detector. The data were collected at a pp collision energy of s = 13 TeV and correspond to an integrated luminosity of 140 fb?1. The measurements use events containing an oppositely charged e? pair and b-tagged jets. The results are compared with predictions from several Monte Carlo generators. While no prediction is found to be consistent with all distributions, a better agreement with measurements of the lepton p T distributions is obtained by reweighting the tt¯ sample so as to reproduce the top-quark p T distribution from an NNLO calculation. The inclusive top-quark pair production cross-section is measured as well, both in a fiducial region and in the full phase-space. The total inclusive cross-section is found to be ?tt¯=829±1(stat)±13(syst)±8(lumi)±2(beam)pb, where the uncertainties are due to statistics, systematic effects, the integrated luminosity and the beam energy. This is in excellent agreement with the theoretical expectation. [Figure not available: see fulltext.] © 2023, The Author(s).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 Measurement of exclusive pion pair production in proton–proton collisions at ?s=7TeV with the ATLAS detector(Institute for Ionics, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliThe exclusive production of pion pairs in the process pp? pp?+?- has been measured at s=7TeV with the ATLAS detector at the LHC, using 80?b-1 of low-luminosity data. The pion pairs were detected in the ATLAS central detector while outgoing protons were measured in the forward ATLAS ALFA detector system. This represents the first use of proton tagging to measure an exclusive hadronic final state at the LHC. A cross-section measurement is performed in two kinematic regions defined by the proton momenta, the pion rapidities and transverse momenta, and the pion–pion invariant mass. Cross-section values of 4.8±1.0(stat)-0.2+0.3(syst)?b and 9±6(stat)-2+2(syst)?b are obtained in the two regions; they are compared with theoretical models and provide a demonstration of the feasibility of measurements of this type. © 2023, The Author(s).Öğe Measurement of Suppression of Large-Radius Jets and Its Dependence on Substructure in Pb+Pb Collisions at ?sNN=5.02 TeV with the ATLAS Detector(American Physical Society, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliThis letter presents a measurement of the nuclear modification factor of large-radius jets in Formula Presented Formula Presented collisions by the ATLAS experiment. The measurement is performed using Formula Presented and Formula Presented of Formula Presented and Formula Presented data, respectively. The large-radius jets are reconstructed with the anti-Formula Presented algorithm using a radius parameter of Formula Presented, by reclustering anti-Formula Presented Formula Presented jets, and are measured over the transverse momentum (Formula Presented) kinematic range of Formula Presented and absolute pseudorapidity Formula Presented. The large-radius jet constituents are further reclustered using the Formula Presented algorithm in order to obtain the splitting parameters, Formula Presented and Formula Presented, which characterize the transverse momentum scale and angular separation for the hardest splitting in the jet, respectively. The nuclear modification factor, Formula Presented, obtained by comparing the Formula Presented jet yields to those in Formula Presented collisions, is measured as a function of jet transverse momentum (Formula Presented) and Formula Presented or Formula Presented. A significant difference in the quenching of large-radius jets having single subjet and those with more complex substructure is observed. Systematic comparison of jet suppression in terms of Formula Presented for different jet definitions is also provided. Presented results support the hypothesis that jets with hard internal splittings lose more energy through quenching and provide a new perspective for understanding the role of jet structure in jet suppression. © 2023 CERN, for the ATLAS Collaboration.Öğe Measurement of the CP properties of Higgs boson interactions with ? -leptons with the ATLAS detector(Institute for Ionics, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliA study of the charge conjugation and parity (CP) properties of the interaction between the Higgs boson and ? -leptons is presented. The study is based on a measurement of CP -sensitive angular observables defined by the visible decay products of ? -leptons produced in Higgs boson decays. The analysis uses 139 fb- 1of proton–proton collision data recorded at a centre-of-mass energy of s=13 TeV with the ATLAS detector at the Large Hadron Collider. Contributions from CP -violating interactions between the Higgs boson and ? -leptons are described by a single mixing angle parameter ??in the generalised Yukawa interaction. Without constraining the H? ?? signal strength to its expected value under the Standard Model hypothesis, the mixing angle ??is measured to be 9?± 16?, with an expected value of 0?± 28?at the 68% confidence level. The pure CP -odd hypothesis is disfavoured at a level of 3.4 standard deviations. The results are compatible with the predictions for the Higgs boson in the Standard Model. © 2023, The Author(s).Öğe Measurement of the properties of Higgs boson production at ?s = 13 TeV in the H ? ?? channel using 139 fb?1 of pp collision data with the ATLAS experiment(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliMeasurements of Higgs boson production cross-sections are carried out in the diphoton decay channel using 139 fb?1 of pp collision data at s = 13 TeV collected by the ATLAS experiment at the LHC. The analysis is based on the definition of 101 distinct signal regions using machine-learning techniques. The inclusive Higgs boson signal strength in the diphoton channel is measured to be 1.04?0.09+0.10 . Cross-sections for gluon-gluon fusion, vector-boson fusion, associated production with a W or Z boson, and top associated production processes are reported. An upper limit of 10 times the Standard Model prediction is set for the associated production process of a Higgs boson with a single top quark, which has a unique sensitivity to the sign of the top quark Yukawa coupling. Higgs boson production is further characterized through measurements of Simplified Template Cross-Sections (STXS). In total, cross-sections of 28 STXS regions are measured. The measured STXS cross-sections are compatible with their Standard Model predictions, with a p-value of 93%. The measurements are also used to set constraints on Higgs boson coupling strengths, as well as on new interactions beyond the Standard Model in an effective field theory approach. No significant deviations from the Standard Model predictions are observed in these measurements, which provide significant sensitivity improvements compared to the previous ATLAS results. [Figure not available: see fulltext.]. © 2023, The Author(s).Öğe Search for a new scalar resonance in flavour-changing neutral-current top-quark decays t ? qX (q = u, c), with X ? bb¯ , in proton-proton collisions at ?s = 13 TeV with the ATLAS detector(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliA search for flavour-changing neutral-current decays of a top quark into an up-type quark (either up or charm) and a light scalar particle X decaying into a bottom anti-bottom quark pair is presented. The search focuses on top-quark pair production where one top quark decays to qX, with X ? bb¯ , and the other top quark decays according to the Standard Model, with the W boson decaying leptonically. The final state is thus characterised by an isolated electron or muon and at least four jets. Events are categorised according to the multiplicity of jets and jets tagged as originating from b-quarks, and a neural network is used to discriminate between signal and background processes. The data analysed correspond to 139 fb?1 of proton–proton collisions at a centre-of-mass energy of 13 TeV, recorded with the ATLAS detector at the LHC. The 95% confidence-level upper limits between 0.019% and 0.062% are derived for the branching fraction B (t ? uX) and between 0.018% and 0.078% for the branching fraction B (t ? cX), for masses of the scalar particle X between 20 and 160 GeV. [Figure not available: see fulltext.] © 2023, The Author(s).Öğe Search for dark photons from Higgs boson decays via ZH production with a photon plus missing transverse momentum signature from pp collisions at ?s = 13 TeV with the ATLAS detector(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliThis paper describes a search for dark photons (?d) in proton-proton collisions at s = 13 TeV at the Large Hadron Collider (LHC). The dark photons are searched for in the decay of Higgs bosons (H ? ??d) produced through the ZH production mode. The transverse mass of the system, made of the photon and the missing transverse momentum from the non-interacting ?d, presents a distinctive signature as it peaks near the Higgs boson mass. The results presented use the total Run-2 integrated luminosity of 139 fb?1 recorded by the ATLAS detector at the LHC. The dominant reducible background processes are estimated using data-driven techniques. A Boosted Decision Tree technique is adopted to enhance the sensitivity of the search. As no excess is observed with respect to the Standard Model prediction, an observed (expected) upper limit on the branching ratio BR(H ? ??d) of 2.28% (2.82?0.84+1.33%) is set at 95% CL for massless ?d. For massive dark photons up to 40 GeV, the observed (expected) upper limits on BR(H ? ??d) at 95% confidence level is found within the [2.19,2.52]% ([2.71,3.11]%) range. [Figure not available: see fulltext.] © 2023, The Author(s).Öğe Search for direct pair production of sleptons and charginos decaying to two leptons and neutralinos with mass splittings near the W-boson mass in ?s = 13 TeV pp collisions with the ATLAS detector(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliA search for the electroweak production of pairs of charged sleptons or charginos decaying into two-lepton final states with missing transverse momentum is presented. Two simplified models of R-parity-conserving supersymmetry are considered: direct pair-production of sleptons (?~ ?~) , with each decaying into a charged lepton and a ?~10 neutralino, and direct pair-production of the lightest charginos (?~1±?~1?) , with each decaying into a W-boson and a ?~10 . The lightest neutralino (?~10) is assumed to be the lightest supersymmetric particle (LSP). The analyses target the experimentally challenging mass regions where m(?~)?m(?~10) and m(?~1±)?m(?~10) are close to the W-boson mass (‘moderately compressed’ regions). The search uses 139 fb?1 of s = 13 TeV proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider. No significant excesses over the expected background are observed. Exclusion limits on the simplified models under study are reported in the (?~?~10) and (?~1±?~10) mass planes at 95% confidence level (CL). Sleptons with masses up to 150 GeV are excluded at 95% CL for the case of a mass-splitting between sleptons and the LSP of 50 GeV. Chargino masses up to 140 GeV are excluded at 95% CL for the case of a mass-splitting between the chargino and the LSP down to about 100 GeV. [Figure not available: see fulltext.] © 2023, 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.Öğe Search for leptonic charge asymmetry in tt¯ W production in final states with three leptons at ?s = 13 TeV(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliA search for the leptonic charge asymmetry (Ac?) of top-quark-antiquark pair production in association with a W boson (tt¯ W) is presented. The search is performed using final states with exactly three charged light leptons (electrons or muons) and is based on s = 13 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider at CERN during the years 2015–2018, corresponding to an integrated luminosity of 139 fb?1. A profile-likelihood fit to the event yields in multiple regions corresponding to positive and negative differences between the pseudorapidities of the charged leptons from top-quark and top-antiquark decays is used to extract the charge asymmetry. At reconstruction level, the asymmetry is found to be ?0.12 ± 0.14 (stat.) ± 0.05 (syst.). An unfolding procedure is applied to convert the result at reconstruction level into a charge-asymmetry value in a fiducial volume at particle level with the result of ?0.11 ± 0.17 (stat.) ± 0.05 (syst.). The Standard Model expectations for these two observables are calculated using Monte Carlo simulations with next-to-leading-order plus parton shower precision in quantum chromodynamics and including next-to-leading-order electroweak corrections. They are ?0.084?0.003+0.005 (scale) ± 0.006 (MC stat.) and ?0.063?0.004+0.007 (scale) ± 0.004 (MC stat.) respectively, and in agreement with the measurements. [Figure not available: see fulltext.]. © 2023, The Author(s).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 A search for new resonances in multiple final states with a high transverse momentum Z boson in ?s = 13 TeV pp collisions with the ATLAS detector(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliA generic search for resonances is performed with events containing a Z boson with transverse momentum greater than 100 GeV, decaying into e + e ? or ? + ? ?. The analysed data collected with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider correspond to an integrated luminosity of 139 fb?1. Two invariant mass distributions are examined for a localised excess relative to the expected Standard Model background in six independent event categories (and their inclusive sum) to increase the sensitivity. No significant excess is observed. Exclusion limits at 95% confidence level are derived for two cases: a model-independent interpretation of Gaussian-shaped resonances with the mass width between 3% and 10% of the resonance mass, and a specific heavy vector triplet model with the decay mode W? ? ZW ? ??qq. [Figure not available: see fulltext.] © 2023, The Author(s).Öğe Search for supersymmetry in final states with missing transverse momentum and three or more b-jets in 139 fb-1 of proton–proton collisions at ?s=13 TeV with the ATLAS detector(Institute for Ionics, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant AliA search for supersymmetry involving the pair production of gluinos decaying via off-shell third-generation squarks into the lightest neutralino (?~10) is reported. It exploits LHC proton–proton collision data at a centre-of-mass energy s=13 TeV with an integrated luminosity of 139 fb - 1 collected with the ATLAS detector from 2015 to 2018. The search uses events containing large missing transverse momentum, up to one electron or muon, and several energetic jets, at least three of which must be identified as containing b-hadrons. Both a simple kinematic event selection and an event selection based upon a deep neural-network are used. No significant excess above the predicted background is found. In simplified models involving the pair production of gluinos that decay via off-shell top (bottom) squarks, gluino masses less than 2.44 TeV (2.35 TeV) are excluded at 95% CL for a massless ?~10. Limits are also set on the gluino mass in models with variable branching ratios for gluino decays to bb¯?~10,tt¯?~10 and tb¯?~1-/t¯b?~1+. © 2023, The Author(s).
