Browsing by Author "Abbott D. C."
A search for heavy Higgs bosons decaying into vector bosons in same-sign two-lepton final states in pp collisions at ?s=13 TeV with the ATLAS detector
(SPRINGER, 2023/07/26) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
A search for heavy Higgs bosons produced in association with a vector boson and decaying into a pair of vector bosons is performed in final states with two leptons (electrons or muons) of the same electric charge, missing transverse momentum and jets. A data sample of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018 is used. The data correspond to a total integrated luminosity of 139 fb(-1). The observed data are in agreement with Standard Model background expectations. The results are interpreted using higher-dimensional operators in an effective field theory. Upper limits on the production cross-section are calculated at 95% confidence level as a function of the heavy Higgs boson's mass and coupling strengths to vector bosons. Limits are set in the Higgs boson mass range from 300 to 1500 GeV, and depend on the assumed couplings. The highest excluded mass for a heavy Higgs boson with the coupling combinations explored is 900 GeV. Limits on coupling strengths are also provided.
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, 2023/06/07) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ahuja S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
A generic search for resonances is performed with events containing a Z boson with transverse momentum greater than 100 GeV, decaying into e(+)e(-) or mu(+)mu(-). The analysed data collected with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13TeV 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 -> llqq.
Anomaly detection search for new resonances decaying into a Higgs boson and a generic new particle X in hadronic final states using ?s=13 TeV pp collisions with the ATLAS detector
(AMER PHYSICAL SOC, 2023/09/18) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
A search is presented for a heavy resonance Y decaying into a Standard Model Higgs boson H and a new particle X in a fully hadronic final state. The full Large Hadron Collider run 2 dataset of proton-proton collisions at root s =13 TeV collected by the ATLAS detector from 2015 to 2018 is used and corresponds to an integrated luminosity of 139 fb(-1). The search targets the high Y-mass region, where the H and X have a significant Lorentz boost in the laboratory frame. A novel application of anomaly detection is used to define a general signal region, where events are selected solely because of their incompatibility with a learned background-only model. It is constructed using a jet-level tagger for signal-model-independent selection of the boosted X particle, representing the first application of fully unsupervised machine learning to an ATLAS analysis. Two additional signal regions are implemented to target a benchmark X decay into two quarks, covering topologies where the X is reconstructed as either a single large-radius jet or two small-radius jets. The analysis selects Higgs boson decays into bb, and a dedicated neural-network-based tagger provides sensitivity to the boosted heavy-flavor topology. No significant excess of data over the expected background is observed, and the results are presented as upper limits on the production cross section sigma(pp -> Y -> XH -> qqbb) for signals with m(Y) between 1.5 and 6 TeV and m(X) between 65 and 3000 GeV.
Calibration of the light-flavour jet mistagging efficiency of the b-tagging algorithms with Z plus jets events using 139 fb-1 of ATLAS proton-proton collision data at ?s=13 TeV
(SPRINGER, 2023/08/14) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
The identification of b-jets, referred to as b-tagging, is an important part of many physics analyses in the ATLAS experiment at the Large Hadron Collider and an accurate calibration of its performance is essential for high-quality physics results. This publication describes the calibration of the light-flavour jet mistagging efficiency in a data sample of proton-proton collision events at root s = 13 TeV corresponding to an integrated luminosity of 139 fb(-1). The calibration is performed in a sample of Z bosons produced in association with jets. Due to the low mistagging efficiency for light-flavour jets, a method which uses modified versions of the b-tagging algorithms referred to as flip taggers is used in this work. A fit to the jet-flavour-sensitive secondary-vertex mass is performed to extract a scale factor from data, to correct the light-flavour jet mistagging efficiency in Monte Carlo simulations, while simultaneously correcting the b-jet efficiency. With this procedure, uncertainties coming from the modeling of jets from heavy-flavour hadrons are considerably lower than in previous calibrations of the mistagging scale factors, where they were dominant. The scale factors obtained in this calibration are consistent with unity within uncertainties.
Constraints on spin-0 dark matter mediators and invisible Higgs decays using ATLAS 13 TeV pp collision data with two top quarks and missing transverse momentum in the final state
(SPRINGER, 2023/06/13) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
This paper presents a statistical combination of searches targeting final states with two top quarks and invisible particles, characterised by the presence of zero, one or two leptons, at least one jet originating from a b-quark and missing transverse momentum. The analyses are searches for phenomena beyond the Standard Model consistent with the direct production of dark matter in pp collisions at the LHC, using 139 fb(-1) of data collected with the ATLAS detector at a centre-of-mass energy of 13 TeV. The results are interpreted in terms of simplified dark matter models with a spin-0 scalar or pseudoscalar mediator particle. In addition, the results are interpreted in terms of upper limits on the Higgs boson invisible branching ratio, where the Higgs boson is produced according to the StandardModel in associationwith a pair of top quarks. For scalar (pseudoscalar) dark matter models, with all couplings set to unity, the statistical combination extends the mass range excluded by the best of the individual channels by 50 (25) GeV, excluding mediator masses up to 370 GeV. In addition, the statistical combination improves the expected coupling exclusion reach by 14% (24%), assuming a scalar (pseudoscalar) mediator mass of 10 GeV. An upper limit on the Higgs boson invisible branching ratio of 0.38 (0.30(-0.09)(+0.13)) is observed (expected) at 95% confidence level.
Constraints on the Higgs boson self-coupling from single- and double-Higgs production with the ATLAS detector using pp collisions at?s=13 TeV
(ELSEVIER, 2023/08/10) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
Constraints on the Higgs boson self-coupling are set by combining double-Higgs boson analyses in the bb over bar bb over bar , bb over bar & tau;+& tau;- and bb over bar & gamma; & gamma; decay channels with single-Higgs boson analyses targeting the & gamma;& gamma;, Z Z*, W W *, & tau;+& tau;- and bb over bar decay channels. The data used in these analyses were recorded by the ATLAS detector at the LHC in proton-proton collisions at & RADIC;s = 13 TeV and correspond to an integrated luminosity of 126-139 fb-1. The combination of the double-Higgs analyses sets an upper limit of & mu;HH < 2.4 at 95% confidence level on the double-Higgs production cross-section normalised to its Standard Model prediction. Combining the single-Higgs and double-Higgs analyses, with the assumption that new physics affects only the Higgs boson self-coupling (& lambda;HHH), values outside the interval -0.4 < & kappa;& lambda; = (& lambda;HHH/& lambda;SM H H H ) < 6.3 are excluded at 95% confidence level. The combined single-Higgs and double-Higgs analyses provide results with fewer assumptions, by adding in the fit more coupling modifiers introduced to account for the Higgs boson interactions with the other Standard Model particles. In this relaxed scenario, the constraint becomes -1.4 < & kappa;& lambda; < 6.1 at 95% CL. & COPY; 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/). Funded by SCOAP3.
Cross-section measurements for the production of a Z boson in association with high-transverse-momentum jets in pp collisions at ?s=13 TeV with the ATLAS detector
(SPRINGER, 2023/06/14) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
Cross-section measurements for a Z boson produced in association with high-transverse-momentum jets ((pT) >= 100 GeV) and decaying into a charged-lepton pair (e(+) e(-), mu(+)mu(-)) are presented. The measurements are performed using proton-proton collisions at root s = 13TeV corresponding to an integrated luminosity of 139 fb(-1) collected by the ATLAS experiment at the LHC. Measurements of angular correlations between the Z boson and the closest jet are performed in events with at least one jet with (pT) >= 500 GeV. Event topologies of particular interest are the collinear emission of a Z boson in dijet events and a boosted Z boson recoiling against a jet. Fiducial cross sections are compared with state-of-the-art theoretical predictions. The data are found to agree with next-to-nextto-leading-order predictions by NNLOjet and with the next-to-leading-order multi-leg generators MadGraph5_aMC@NLO and Sherpa.
Differential t(t)over-tilde cross-section measurements using boosted top quarks in the all-hadronic final state with 139 fb-1 of ATLAS data
(SPRINGER, 2023/04/18) Aad G.; Abbott B.; Abbott D. C.; Abud A. Abed; Abeling K.; Abhayasinghe D. K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Hoffman A. C. Abusleme; Acharya B. S.; Achkar B.; Adam L.; Bourdarios C. Adam; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.
Measurements of single-, double-, and triple-differential cross-sections are presented for boosted top-quark pair-production in 13 TeV proton-proton collisions recorded by the ATLAS detector at the LHC. The top quarks are observed through their hadronic decay and reconstructed as large-radius jets with the leading jet having transverse momentum (p(T)) greater than 500 GeV. The observed data are unfolded to remove detector effects. The particle-level cross-section, multiplied by the t (t) over bar branching fraction and measured in a fiducial phase space defined by requiring the leading and second-leading jets to have p(T)> 500 GeV and p(T)> 350 GeV, respectively, is 331 +/- 3(stat.) +/- 39(syst.) fb. This is approximately 20% lower than the prediction of 398(-49)(+48) fb by Powheg+Pythia 8 with next-to-leading-order (NLO) accuracy but consistent within the theoretical uncertainties. Results are also presented at the parton level, where the effects of top-quark decay, parton showering, and hadronization are removed such that they can be compared with fixed-order next-to-next-to-leading-order (NNLO) calculations. The parton-level cross-section, measured in a fiducial phase space similar to that at particle level, is 1.94 +/- 0.02(stat.) +/- 0.25(syst.) pb. This agrees with the NNLO prediction of 1.96(-0.17)(+0.02) pb. Reasonable agreement with the differential cross-sections is found for most NLO models, while the NNLO calculations are generally in better agreement with the data. The differential cross-sections are interpreted using a Standard Model effective field-theory formalism and limits are set on Wilson coefficients of several four-fermion operators.
Evidence for the charge asymmetry in pp ? t(t)over-bar production at ?s=13 TeV with the ATLAS detector
(SPRINGER, 2023/08/16) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
Inclusive and differential measurements of the top-antitop ( t (t) over bar) charge asymmetry A(C)(t (t) over bar) and the leptonic asymmetry A(C)(l (l) over bar) are presented in proton-proton collisions at root s = 13 TeV recorded by the ATLAS experiment at the CERN Large Hadron Collider. The measurement uses the complete Run 2 dataset, corresponding to an integrated luminosity of 139 fb(-1), combines data in the single-lepton and dilepton channels, and employs reconstruction techniques adapted to both the resolved and boosted topologies. A Bayesian unfolding procedure is performed to correct for detector resolution and acceptance effects. The combined inclusive t (t) over bar charge asymmetry is measured to be A(C)(t (t) over bar) = 0.0068 +/- 0.0015, which differs from zero by 4.7 standard deviations. Differential measurements are performed as a function of the invariant mass, transverse momentum and longitudinal boost of the t (t) over bar system. Both the inclusive and differential measurements are found to be compatible with the Standard Model predictions, at next-to-next-to-leading order in quantum chromodynamics perturbation theory with next-to-leading-order electroweak corrections. The measurements are interpreted in the framework of the Standard Model effective field theory, placing competitive bounds on several Wilson coefficients.
Exclusive dielectron production in ultraperipheral Pb plus Pb collisions at ?sNN=5.02 TeV with ATLAS
(SPRINGER, 2023/06/27) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
Exclusive production of dielectron pairs, gamma gamma -> e(+) e(-), is studied using L-int = 1.72 nb(-1) of data from ultraperipheral collisions of lead nuclei at root s(NN) = 5.02TeV recorded by the ATLAS detector at the LHC. The process of interest proceeds via photon-photon interactions in the strong electromagnetic fields of relativistic lead nuclei. Dielectron production is measured in the fiducial region defined by following requirements: electron transverse momentum p(T)(e) > 2.5 GeV, absolute electron pseudorapidity |eta(e)| < 2.5, dielectron invariant mass m(ee) > 5 GeV, and dielectron transverse momentum p(T)(ee) < 2 GeV. Differential cross-sections are measured as a function of mee, average peT, absolute dielectron rapidity |y(ee)|, and scattering angle in the dielectron rest frame, | cos theta* |, in the inclusive sample, and also with a requirement of no activity in the forward direction. The total integrated fiducial cross-section is measured to be 215 +/- 1(stat.) (+23)(-20)(syst.) +/- 4(lumi.) mu b. Within experimental uncertainties the measured integrated cross-section is in good agreement with the QED predictions from the Monte Carlo programs Starlight and SuperChic, confirming the broad features of the initial photon fluxes. The differential cross-sections show systematic differences from these predictions which are more pronounced at high |y(ee)| and | cos theta* | values.
Measurement of electroweak Z(v (v)over-bar)? jj production and limits on anomalous quartic gauge couplings in pp collisions at ?s=13 TeV with the ATLAS detector
(SPRINGER, 2023/06/14) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
The electroweak production of Z(v (v) over bar)gamma in association with two jets is studied in a regime with a photon of high transverse momentum above 150 GeV using proton-proton collisions at a centre-of-mass energy of 13TeV at the Large Hadron Collider. The analysis uses a data sample with an integrated luminosity of 139 fb(-1) collected by the ATLAS detector during the 2015-2018 LHC data-taking period. This process is an important probe of the electroweak symmetry breaking mechanism in the Standard Model and is sensitive to quartic gauge boson couplings via vector-boson scattering. The fiducial Z( v (v) over bar)gamma jj cross section for electroweak production is measured to be 0.77(-0.30)(+0.34) fb and is consistent with the Standard Model prediction. Evidence of electroweak Z( v (v) over bar)gamma jj production is found with an observed significance of 3.2 sigma for the background-only hypothesis, compared with an expected significance of 3.7 sigma. The combination of this result with the previously published ATLAS observation of electroweak Z(v (v) over bar)gamma jj production yields an observed (expected) signal significance of 6.3 sigma (6.6 sigma). Limits on anomalous quartic gauge boson couplings are obtained in the framework of effective field theory with dimension-8 operators.
Measurement of exclusive pion pair production in proton-proton collisions at ?s=7 TeV with the ATLAS detector
(SPRINGER, 2023/07/17) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
The exclusive production of pion pairs in the process pp -> pp pi(+)pi(-) has been measured at root s = 7TeV with the ATLAS detector at the LHC, using 80 mu b(-1) of low-luminosity data. The pion pairs were detected in the ATLAS central detector while outgoing protons were measured in the forwardATLASALFAdetector system. This represents the first use of proton tagging to measure an exclusive hadronic final state at the LHC. Across-sectionmeasurement 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) mu b and 9 +/- 6 (stat)(-2)(+2) (syst) mu 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.
Measurement of single top-quark production in the s-channel in proton-proton collisions at ?s=13 TeV with the ATLAS detector
(SPRINGER, 2023/06/27) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
A measurement of single top-quark production in the s-channel is performed in proton-proton collisions at a centre-of-mass energy of 13TeV with the ATLAS detector at the CERN Large Hadron Collider. The dataset corresponds to an integrated luminosity of 139 fb(-1). The analysis is performed on events with an electron or muon, missing transverse momentum and exactly two b-tagged jets in the final state. A discriminant based on matrix element calculations is used to separate single-top-quark s-channel events from the main background contributions, which are top-quark pair production and W-boson production in association with jets. The observed (expected) signal significance over the background-only hypothesis is 3.3 (3.9) standard deviations, and the measured cross-section is sigma = 8.2(-2.9)(+3.5) pb, consistent with the Standard Model prediction of sigma(SM) = 10.32(-0.36)(+0.40) pb.
Measurement of the charge asymmetry in top-quark pair production in association with a photon with the ATLAS experiment
(ELSEVIER, 2023/08/10) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
A measurement of the charge asymmetry in top-quark pair (t (t) over bar) production in association with a photon is presented. The measurement is performed in the single-lepton t (t) over bar decay channel using proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider at CERN at a centre-of-mass-energy of 13 TeV during the years 2015-2018, corresponding to an integrated luminosity of 139 fb(-1). The charge asymmetry is obtained from the distribution of the difference of the absolute rapidities of the top quark and antiquark using a profile likelihood unfolding approach. It is measured to be A(C) = -0.003 +/- 0.029 in agreement with the Standard Model expectation. (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/).
Measurement of the Higgs boson mass in the H?ZZ* ? 4l decay channel using 139 fb-1 of ?s=13 TeV pp collisions recorded by the ATLAS detector at the LHC
(ELSEVIER, 2023/08/10) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ahuja S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
The mass of the Higgs boson is measured in the H -> Z Z* -> 4l decay channel. The analysis uses proton-proton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector between 2015 and 2018, corresponding to an integrated luminosity of 139 fb(-1). The measured value of the Higgs boson mass is 124.99 0.18(stat.) +/- 0.04(syst.) GeV. In final states with muons, this measurement benefits from an improved momentum-scale calibration relative to that adopted in previous publications. The measurement also employs an analytic model that takes into account the invariant-mass resolution of the four-lepton system on a per-event basis and the output of a deep neural network discriminating signal from background events. This measurement is combined with the corresponding measurement using 7 and 8 TeV pp collision data, resulting in a Higgs boson mass of 124.94 +/- 0.17(stat.) +/- 0.03(syst.) GeV. (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/). Funded by SCOAP3.
Measurement of the nuclear modification factor of b-jets in 5.02 TeV Pb+Pb collisions with the ATLAS detector
(SPRINGER, 2023/05/25) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
This paper presents a measurement of b-jet production in Pb+Pb and pp collisions at root s(NN) = 5.02 TeV with the ATLAS detector at the LHC. The measurement uses 260 pb(-1) of pp collisions collected in 2017 and 1.4 nb(-1) of Pb+Pb collisions collected in 2018. In both collision systems, jets are reconstructed via the anti-kt algorithm. The b-jets are identified from a sample of jets containing muons from the semileptonic decay of b-quarks using template fits of the muon momentum relative to the jet axis. In pp collisions, b-jets are reconstructed for radius parameters R=0.2 and R=0.4, and only R=0.2 jets are used in Pb+Pb collisions. For comparison, inclusive R=0.2 jets are also measured using 1.7 nb(-1) of Pb+Pb collisions collected in 2018 and the same pp collision data as the b-jet measurement. The nuclear modification factor, RAA, is calculated for both b-jets and inclusive jets with R=0.2 over the transverse momentum range of 80-290 GeV. The nuclear modification factor for b-jets decreases from peripheral to central collisions. The ratio of the b-jet RAA to inclusive jet RAA is also presented and suggests that the RAA for b-jets is larger than that for inclusive jets in central Pb+Pb collisions. The measurements are compared with theoretical calculations and suggest a role for mass and colour-charge effects in partonic energy loss in heavy-ion collisions.
Measurement of the polarisation of Wbosons produced in top-quark decays using dilepton events at ?s=13TeV with the ATLAS experiment
(ELSEVIER, 2023/08/10) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhormae A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffmana A. C.; Acharyaa B. S.; Bourdarios C. Adam; Adamczyka L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzelc A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwalaa J.; Aggarwal A.; Agheorghieseic C.; Aguilar-Saavedraf J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ahuja S.; Ai X.; Aiellia G.; Tamlihate M. Ait; Aitbenchikh B.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghib G. L.
A measurement of the polarisation of Wbosons produced in top-quark decays is presented, using proton-proton collision data at a centre-of-mass energy of v s= 13TeV. The data were collected by the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 139fb(-1). The measurement is performed selecting t tevents decaying into final states with two charged leptons (electrons or muons) and at least two b-tagged jets. The polarisation is extracted from the differential cross-section distribution of the cos theta* variable, where theta(*) is the angle between the momentum direction of the charged lepton from the Wboson decay and the reversed momentum direction of the b-quark from the top-quark decay, both calculated in the Wboson rest frame. Parton-level results, corrected for the detector acceptance and resolution, are presented for the cos theta* angle. The measured fractions of longitudinal, left- and right-handed polarisation states are found to be f(0) = 0.684 +/- 0.005 (stat.)+/- 0.014 (syst.), f(L)= 0.318 +/- 0.003 (stat.)+/- 0.008 (syst.) and f(R)=-0.002 +/- 0.002 (stat.)+/- 0.014 (syst.), in agreement with the Standard Model prediction. (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/). Funded by SCOAP(3).
Measurement of the t(t)over-bar production cross-section in pp collisions at ?s=5.02 TeV with the ATLAS detector
(SPRINGER, 2023/06/23) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
The inclusive top-quark pair ( t (t) over bar) production cross-section sigma(t (t) over bar) is measured in proton-proton collisions at a centre-of-mass energy root s = 5.02TeV, using 257 pb(-1) of data collected in 2017 by the ATLAS experiment at the LHC. The tt (t) over bar cross-section is measured in both the dilepton and single-lepton final states of the t t system and then combined. The combination of the two measurements yields sigma(t (t) over bar) = 67.5 +/- 0.9 (stat.) +/- 2.3 (syst.) +/- 1.1 (lumi.) +/- 0.2 (beam) pb, where the four uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, and imperfect knowledge of both the integrated luminosity and the LHC beam energy, giving a total uncertainty of 3.9%. The result is in agreement with theoretical quantum chromodynamic calculations at next-to-next-to-leading order in the strong coupling constant, including the resummation of next-to-next-to-leading logarithmic soft-gluon terms, and constrains the parton distribution functions of the proton at large Bjorken-x.
Measurement of the total and differential Higgs boson production cross-sections at ?s=13 TeV with the ATLAS detector by combining the H ? ZZ*? 4l and H ? ?? decay channels
(SPRINGER, 2023/05/04) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
The total and differential Higgs boson production cross-sections are measured through a combined statistical analysis of the H -> ZZ(*) -> 4l and H -> gamma gamma decay channels. The results are based on a dataset of 139 fb(-1) of proton-proton collisions at a centre-of-mass energy of 13 TeV, recorded by the ATLAS detector at the Large Hadron Collider. The measured total Higgs boson production cross-section is 55.5(-3.8)(+4.0) pb, consistent with the Standard Model prediction of 55.6 +/- 2.5 pb. All results from the two decay channels are compatible with each other, and their combination agrees with the Standard Model predictions. A combined statistical interpretation of the measured fiducial cross-sections as a function of the Higgs boson transverse momentum is performed in order to probe the Yukawa couplings to the bottom and charm quarks. A similar interpretation is performed by including also the constraints from the measurements of Higgs boson production in association with a W or Z boson in the H -> b (b) over bar and c (c) over bar decay channels.
Measurement of the total cross section and ?-parameter from elastic scattering in pp collisions at ?s=13 TeV with the ATLAS detector
(SPRINGER, 2023/05/26) Aad G.; Abbott B.; Abbott D. C.; Abeling K.; Abidi S. H.; Aboulhorma A.; Abramowicz H.; Abreu H.; Abulaiti Y.; Abusleme Hoffman A. C.; Acharya B. S.; Achkar B.; Adam L.; Adam Bourdarios C.; Adamczyk L.; Adamek L.; Addepalli S. V.; Adelman J.; Adiguzel A.; Adorni S.; Adye T.; Affolder A. A.; Afik Y.; Agaras M. N.; Agarwala J.; Aggarwal A.; Agheorghiesei C.; Aguilar-Saavedra J. A.; Ahmad A.; Ahmadov F.; Ahmed W. S.; Ai X.; Aielli G.; Aizenberg I.; Akbiyik M.; Akesson T. P. A.; Akimov A. V.; Al Khoury K.; Alberghi G. L.; Albert J.
In a special run of the LHC with beta star=2.5 km, proton-proton elastic-scattering events were recorded at root s=13 TeV with an integrated luminosity of 340 mu b(-1) using the ALFA subdetector of ATLAS in 2016. The elastic cross section was measured differentially in the Mandelstam t variable in the range from -t=2.5 center dot 10(-4) GeV2 to -t=0.46 GeV2 using 6.9 million elastic-scattering candidates. This paper presents measurements of the total cross section sigma(tot), parameters of the nuclear slope, and the rho-parameter defined as the ratio of the real part to the imaginary part of the elastic-scattering amplitude in the limit t -> 0. These parameters are determined from a fit to the differential elastic cross section using the optical theorem and different parameterizations of the t-dependence. The results for sigma(tot) and rho are sigma(tot) (PP -> X ) =104.7 +/- 1.1 mob , rho=0.098 +/- 0.011. The uncertainty in sigma(tot) is dominated by the luminosity measurement, and in rho by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.