L. Zwalinski

• European Organization for Nuclear Research

Higgsinos with masses near the electroweak scale can solve the hierarchy problem and provide a dark matter candidate, while detecting them at the LHC remains challenging if their mass splitting is O ( 1 GeV ) . This Letter presents a novel search for nearly mass-degenerate Higgsinos in events with an energetic jet, missing transverse momentum, and...

A bstract The production of single top quarks and top antiquarks via the t -channel exchange of a virtual W boson is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV at the LHC using 140 fb − 1 of ATLAS data. The total cross-sections are determined to be $$ \sigma (tq)={137}_{-8}^{+8} $$ σ tq = 137 − 8 + 8 pb and $$ \sigma...

The ATLAS detector is installed in its experimental cavern at Point 1 of the CERN Large Hadron Collider. During Run 2 of the LHC, a luminosity of ℒ = 2 × 10 ³⁴ cm ⁻² s ⁻¹ was routinely achieved at the start of fills, twice the design luminosity. For Run 3, accelerator improvements, notably luminosity levelling, allow sustained running at an instant...

A bstract A search for events with one top quark and missing transverse momentum in the final state is presented. The fully hadronic decay of the top quark is explored by selecting events with a reconstructed boosted top-quark topology produced in association with large missing transverse momentum. The analysis uses 139 fb − 1 of proton-proton coll...

We present performance studies of the Time-of-Flight (ToF) subdetector of the ATLAS Forward Proton (AFP) detector at the LHC. Efficiencies and resolutions are measured using high-statistics data samples collected at low and moderate pile-up in 2017, the first year when the detectors were installed on both sides of the interaction region. While low...

Angular correlations between heavy quarks provide a unique probe of the quark-gluon plasma created in ultrarelativistic heavy-ion collisions. Results are presented of a measurement of the azimuthal angle correlations between muons originating from semileptonic decays of heavy quarks produced in 5.02 TeV Pb + Pb and p p collisions at the LHC. The mu...

A bstract Measurements of inclusive and differential production cross-sections of a top-quark-top-antiquark pair in association with a W boson ( $$ t\overline{t}W $$ t t ¯ W ) are presented. They are performed by targeting final states with two same-sign or three isolated leptons (electrons or muons) and are based on $$ \sqrt{s} $$ s = 13 TeV proto...

Clusters of topologically connected calorimeter cells around cells with large absolute signal-to-noise ratio ( topo-clusters ) are the basis for calorimeter signal reconstruction in the ATLAS experiment. Topological cell clustering has proven performant in LHC Runs 1 and 2. It is, however, susceptible to out-of-time pile-up of signals from soft col...

A bstract A search for R-parity-violating supersymmetry in final states with high jet multiplicity is presented. The search uses 140 fb − 1 of proton-proton collision data at $$ \sqrt{s} $$ s = 13 TeV collected by the ATLAS experiment during Run 2 of the Large Hadron Collider. The results are interpreted in the context of R-parity-violating supersy...

A bstract A summary of the constraints from searches performed by the ATLAS collaboration for the electroweak production of charginos and neutralinos is presented. Results from eight separate ATLAS searches are considered, each using 140 fb − 1 of proton-proton data at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV collected at the Large Hadr...

A bstract Three searches for the direct production of τ -sleptons or charginos and neutralinos in final states with at least two hadronically decaying τ -leptons are presented. For chargino and neutralino production, decays via intermediate τ -sleptons or W and h bosons are considered. The analysis uses a dataset of pp collisions corresponding to a...

A bstract Precision measurements of electron reconstruction, identification, and isolation efficiencies and photon identification efficiencies are presented. They use the full Run 2 data sample collected by the ATLAS experiment in pp collisions at a centre-of-mass energy of 13 TeV during the years 2015–2018, corresponding to an integrated luminosit...

A bstract A combination of searches for new heavy spin-1 resonances decaying into different pairings of W , Z , or Higgs bosons, as well as directly into leptons or quarks, is presented. The data sample used corresponds to 139 fb − 1 of proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV collected during 2015–2018 with the ATLAS detector at the C...

A bstract This paper presents the measurement of fiducial and differential cross sections for both the inclusive and electroweak production of a same-sign W -boson pair in association with two jets ( W ± W ± jj ) using 139 fb − 1 of proton-proton collision data recorded at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV by the ATLAS detector a...

Charged particle reconstruction in the presence of many simultaneous proton–proton (pp\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p {} p $$\end{document}) collision...

This Letter presents the first study of Higgs boson production in association with a vector boson ( V = W or Z ) in the fully hadronic q q b b final state using data recorded by the ATLAS detector at the LHC in proton-proton collisions at s = 13 TeV and corresponding to an integrated luminosity of 137 fb − 1 . The vector bosons and Higgs bosons are...

A bstract A search is conducted for new phenomena in events with a top quark pair and large missing transverse momentum, where the top quark pair is reconstructed in final states with one isolated electron or muon and multiple jets. The search is performed using the Large Hadron Collider proton-proton collision data sample at a centre-of-mass energ...

ATLAS measured the centrality dependence of the dijet yield using 165 nb − 1 of p + Pb data collected at s NN = 8.16 TeV in 2016. The event centrality, which reflects the p + Pb impact parameter, is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled...

This paper presents for the first time a precise measurement of the production properties of the Z boson in the full phase space of the decay leptons. This is in contrast to the many previous precise unfolded measurements performed in the fiducial phase space of the decay leptons. The measurement is obtained from proton–proton collision data collec...

A bstract A search for a heavy CP-odd Higgs boson, A , decaying into a Z boson and a heavy CP-even Higgs boson, H , is presented. It uses the full LHC Run 2 dataset of pp collisions at $$ \sqrt{s} $$ s = 13 TeV collected with the ATLAS detector, corresponding to an integrated luminosity of 140 fb − 1 . The search for A → ZH is performed in the $$ {...

Searches for new resonances are performed using an unsupervised anomaly-detection technique. Events with at least one electron or muon are selected from 140 fb − 1 of p p collisions at s = 13 TeV recorded by ATLAS at the Large Hadron Collider. The approach involves training an autoencoder on data, and subsequently defining anomalous regions based o...

A bstract A search for non-resonant Higgs boson pair ( HH ) production is presented, in which one of the Higgs bosons decays to a b -quark pair ( $$ b\overline{b} $$ b b ¯ ) and the other decays to WW * , ZZ * , or τ ⁺ τ − , with in each case a final state with ℓ ⁺ ℓ − + neutrinos ( ℓ = e, μ ). The analysis targets separately the gluon-gluon fusion...

A search for the associated production of a heavy resonance with a top-quark or a top-antitop-quark pair, and decaying into a \(t{\bar{t}}\) pair is presented. The search uses the data recorded by the ATLAS detector in pp collisions at \(\sqrt{s}= 13\) \(\text {TeV}\) at the Large Hadron Collider during the years 2015–2018, corresponding to an inte...

A bstract A search for pair production of squarks or gluinos decaying via sleptons or weak bosons is reported. The search targets a final state with exactly two leptons with same-sign electric charge or at least three leptons without any charge requirement. The analysed data set corresponds to an integrated luminosity of 139 fb − 1 of proton-proton...

Measurements of the differential production cross-sections of prompt and non-prompt \(J/\psi \) and \(\psi (2{\textrm{S}})\) mesons with transverse momenta between 8 and 360 GeV and rapidity in the range \(|y|<2\) are reported. Furthermore, measurements of the non-prompt fractions of \(J/\psi \) and \(\psi (2{\textrm{S}})\), and the prompt and non-...

A bstract This paper presents a search for a new Z ′ resonance decaying into a pair of dark quarks which hadronise into dark hadrons before promptly decaying back as Standard Model particles. This analysis is based on proton-proton collision data recorded at $$ \sqrt{s} $$ s = 13 TeV with the ATLAS detector at the Large Hadron Collider between 2015...

This paper presents a study of \(Z \rightarrow ll\gamma \) decays with the ATLAS detector at the Large Hadron Collider. The analysis uses a proton–proton data sample corresponding to an integrated luminosity of 20.2 fb\(^{-1}\) collected at a centre-of-mass energy \(\sqrt{s}\) = 8 TeV. Integrated fiducial cross-sections together with normalised dif...

The inclusive Higgs boson production cross-section is measured in the di-photon and the \(ZZ^* \rightarrow 4 \ell \) decay channels using 31.4 and 29.0 fb\(^{-1}\) of pp collision data respectively, collected with the ATLAS detector at a centre-of-mass energy of \(\sqrt{s}=13.6\) \(\text {TeV}\). To reduce the model dependence, the measurement in e...

A bstract A search for nonresonant Higgs boson pair production in the $$ b\overline{b}\gamma \gamma $$ b b ¯ γγ final state is performed using 140 fb − 1 of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. This analysis supersedes and expands upon the previous nonresonan...

The first evidence for the Higgs boson decay to a Z boson and a photon is presented, with a statistical significance of 3.4 standard deviations. The result is derived from a combined analysis of the searches performed by the ATLAS and CMS Collaborations with proton-proton collision datasets collected at the CERN Large Hadron Collider (LHC) from 201...

This Letter reports the observation of W Z γ production and a measurement of its cross section using 140.1 ± 1.2 fb − 1 of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The W Z γ production cross section, with both the W and Z bosons decaying leptonically, p p → W Z γ...

A bstract Differential cross-sections are measured for the production of four charged leptons in association with two jets. These measurements are sensitive to final states in which the jets are produced via the strong interaction as well as to the purely-electroweak vector boson scattering process. The analysis is performed using proton-proton col...

A bstract A search for flavour-changing neutral interactions involving the top quark, the Higgs boson and an up-type quark q ( q = c, u ) is presented. The proton-proton collision data set used, with an integrated luminosity of 139 fb − 1 , was collected at $$ \sqrt{s} $$ s = 13 TeV by the ATLAS experiment at the Large Hadron Collider. Both the dec...

Searches for electroweak production of wino-like chargino pairs, \( {\overset{\sim }{\chi}}_1^{+}{\overset{\sim }{\chi}}_1^{-} \), and of wino-like chargino and next-to-lightest neutralino, \( {\overset{\sim }{\chi}}_1^{\pm }{\overset{\sim }{\chi}}_2^0 \), are presented. The models explored assume that the charginos decay into a W boson and the lig...

A measurement of the mass of the Higgs boson combining the H→ZZ*→4ℓ and H→γγ decay channels is presented. The result is based on 140 fb−1 of proton-proton collision data collected by the ATLAS detector during LHC run 2 at a center-of-mass energy of 13 TeV combined with the run 1 ATLAS mass measurement, performed at center-of-mass energies of 7 and...

A search for events with a dark photon produced in association with a dark Higgs boson via rare decays of the standard model Z boson is presented, using 139 fb−1 of s=13 TeV proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider. The dark boson decays into a pair of dark photons, and at least two of the three dark...

A bstract A study of the polarisation and CP properties in ZZ production is presented. The used data set corresponds to an integrated luminosity of 140 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 ZZ candidate events are reconstructed using two same-flavour...

A bstract A search for a new massive charged gauge boson, W ′, is performed with the ATLAS detector at the LHC. The dataset used in this analysis was collected from proton-proton collisions at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV, and corresponds to an integrated luminosity of 139 fb − 1 . The reconstructed tb invariant mass is used...

A bstract A search for new heavy scalars with flavour-violating decays in final states with multiple leptons and b -tagged jets is presented. The results are interpreted in terms of a general two-Higgs-doublet model involving an additional scalar with couplings to the top-quark and the three up-type quarks ( ρ tt , ρ tc , and ρ tu ). The targeted s...

A bstract A search is presented for single production of a vector-like B quark decaying into a Standard Model b -quark and a Standard Model Higgs boson, which decays into a $$ b\overline{b} $$ b b ¯ pair. The search is carried out in 139 fb − 1 of $$ \sqrt{s} $$ s = 13 TeV proton-proton collision data collected by the ATLAS detector at the LHC betw...

A bstract A search for supersymmetry targeting the direct production of winos and higgsinos is conducted in final states with either two leptons ( e or μ ) with the same electric charge, or three leptons. The analysis uses 139 fb − 1 of pp collision data at $$ \sqrt{s} $$ s = 13 TeV collected with the ATLAS detector during Run 2 of the Large Hadron...

A bstract We present a search for magnetic monopoles and high-electric-charge objects using LHC Run 2 $$ \sqrt{s} $$ s = 13 TeV proton-proton collisions recorded by the ATLAS detector. A total integrated luminosity of 138 fb − 1 was collected by a specialized trigger. No highly ionizing particle candidate was observed. Considering the Drell-Yan and...

This Letter reports the observation of single top quarks produced together with a photon, which directly probes the electroweak coupling of the top quark. The analysis uses 139 fb−1 of 13 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. Requiring a photon with transverse momentum larger than 20 GeV an...

A search for pair-produced scalar or vector leptoquarks decaying into a b-quark and a \(\tau \)-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 \(\sqrt{s} =13\) TeV. Events in which at least one \(\tau \)-lepton decays...

Searches for long-lived particles (LLPs) are among the most promising avenues for discovering physics beyond the Standard Model at the Large Hadron Collider (LHC). However, displaced signatures are notoriously difficult to identify due to their ability to evade standard object reconstruction strategies. In particular, the ATLAS track reconstruction...

This letter presents a measurement of the nuclear modification factor of large-radius jets in sNN=5.02 TeV Pb+Pb collisions by the ATLAS experiment. The measurement is performed using 1.72 nb−1 and 257 pb−1 of Pb+Pb and pp data, respectively. The large-radius jets are reconstructed with the anti-kt algorithm using a radius parameter of R=1.0, by re...

A key open question in the study of multiparticle production in high-energy pp collisions is the relationship between the “ridge”—i.e., the observed azimuthal correlations between particles in the underlying event that extend over all rapidities—and hard or semihard scattering processes. In particular, it is not known whether jets or their soft fra...

A bstract A search for physics beyond the Standard Model inducing periodic signals in the dielectron and diphoton invariant mass spectra is presented using 139 fb − 1 of $$ \sqrt{s} $$ s = 13 TeV pp collision data collected by the ATLAS experiment at the LHC. Novel search techniques based on continuous wavelet transforms are used to infer the frequ...

A bstract A search is performed for a heavy particle decaying into different-flavour, dilepton final states, using 139 fb − 1 of proton-proton collision data at $$ \sqrt{s} $$ s = 13 TeV collected in 2015–2018 by the ATLAS detector at the Large Hadron Collider. Final states with electrons, muons and hadronically decaying tau leptons are considered...

This Letter reports the observation of τ-lepton-pair production in ultraperipheral lead-lead collisions Pb+Pb→Pb(γγ→ττ)Pb and constraints on the τ-lepton anomalous magnetic moment a_{τ}. The dataset corresponds to an integrated luminosity of 1.44 nb^{-1} of LHC Pb+Pb collisions at sqrt[s_{NN}]=5.02 TeV recorded by the ATLAS experiment in 2018. Sele...

A search is made for potential ccc[over ¯]c[over ¯] tetraquarks decaying into a pair of charmonium states in the four muon final state using proton-proton collision data at sqrt[s]=13 TeV, corresponding to an integrated luminosity of 140 fb^{-1} recorded by the ATLAS experiment at LHC. Two decay channels, J/ψ+J/ψ→4μ and J/ψ+ψ(2S)→4μ, are studied. B...

A bstract A measurement of novel event shapes quantifying the isotropy of collider events is performed in 140 fb − 1 of proton-proton collisions with $$ \sqrt{s} $$ s = 13 TeV centre-of-mass energy recorded with the ATLAS detector at CERN’s Large Hadron Collider. These event shapes are defined as the Wasserstein distance between collider events and...

A bstract A search for a new heavy scalar particle X decaying into a Standard Model (SM) Higgs boson and a new singlet scalar particle S is presented. The search uses a proton-proton ( pp ) collision data sample with an integrated luminosity of 140 fb − 1 recorded at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV with the ATLAS detector at th...

A bstract A search for leptoquarks decaying into the bτ final state is performed using Run 2 proton-proton collision data from the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb − 1 at $$ \sqrt{s} $$ s = 13 TeV recorded by the ATLAS detector. The benchmark models considered in this search are vector leptoquarks with elec...

The luminosity determination for the ATLAS detector at the LHC during Run 2 is presented, with pp collisions at a centre-of-mass energy \(\sqrt{s}=13\) 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 comp...

A bstract This paper reports the first ATLAS measurement of the $$ {B}_s^0 $$ B s 0 → μμ effective lifetime. The measurement is based on the data collected in 2015–2016, amounting to 26.3 fb − 1 of 13 TeV LHC proton-proton collisions. The proper decay-time distribution of 58 ± 13 background-subtracted signal candidates is fit with simulated signal...

A bstract A search for dark matter produced in association with a Higgs boson in final states with two hadronically decaying τ -leptons and missing transverse momentum is presented. The analysis uses 139 fb − 1 of proton-proton collision data at $$ \sqrt{s} $$ s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 an...

A bstract A search for a charged Higgs boson, H ± , produced in top-quark decays, t → H ± b , is presented. The search targets H ± decays into a bottom and a charm quark, H ± → cb . The analysis focuses on a selection enriched in top-quark pair production, where one top quark decays into a leptonically decaying W boson and a bottom quark, and the o...

A bstract This 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 $$ \sqrt{s} $$ s = 13 TeV collected with the ATLAS detector during the 2015–2018 data-taking period of the Large Hadron Collider, corresponding to an integrated lumi...

Jet quenching is the process of color-charged partons losing energy via interactions with quark-gluon plasma droplets created in heavy-ion collisions. The collective expansion of such droplets is well described by viscous hydrodynamics. Similar evidence of collectivity is consistently observed in smaller collision systems, including pp and p+Pb col...

A bstract Inclusive and differential measurements of the top–antitop ( $$ t\overline{t} $$ t t ¯ ) charge asymmetry $$ {A}_{\textrm{C}}^{t\overline{t}} $$ A C t t ¯ and the leptonic asymmetry $$ {A}_{\textrm{C}}^{\ell \overline{\ell}} $$ A C ℓ ℓ ¯ are presented in proton–proton collisions at $$ \sqrt{s} $$ s = 13 TeV recorded by the ATLAS experimen...

A test of CP invariance in Higgs boson production via vector-boson fusion has been performed in the H→γγ channel using 139 fb^{-1} of proton-proton collision data at sqrt[s]=13 TeV collected by the ATLAS detector at the LHC. The optimal observable method is used to probe the CP structure of interactions between the Higgs boson and electroweak gauge...

A bstract A search for forward proton scattering in association with light-by-light scattering mediated by an axion-like particle is presented, using the ATLAS Forward Proton spectrometer to detect scattered protons and the central ATLAS detector to detect pairs of outgoing photons. Proton-proton collision data recorded in 2017 at a centre-of-mass...

A bstract A combination of measurements of the inclusive top-quark pair production cross-section performed by ATLAS and CMS in proton–proton collisions at centre-of-mass energies of 7 and 8 TeV at the LHC is presented. The cross-sections are obtained using top-quark pair decays with an opposite-charge electron–muon pair in the final state and with...

A bstract A 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 → $$ b\overline{b} $$ b b ¯ , and the other top q...

A bstract A search for a new heavy scalar or pseudo-scalar Higgs boson ( H/A ) produced in association with a pair of top quarks, with the Higgs boson decaying into a pair of top quarks ( H/A → $$ t\overline{t} $$ t t ¯ ) is reported. The search targets a final state with exactly two leptons with same-sign electric charges or at least three leptons...

A bstract A search for resonances in events with at least one isolated lepton ( e or μ ) and two jets is performed using 139 fb − 1 of $$ \sqrt{s} $$ s = 13 TeV proton–proton collision data recorded by the ATLAS detector at the LHC. Deviations from a smoothly falling background hypothesis are tested in three- and four-body invariant mass distributi...

A bstract 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...

A bstract A 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 $$ \sqrt{s} $$ s = 13 TeV pp collision data recorded by the ATLAS detector at the Large Hadron Collider at CERN. This search examines 22 final states categori...

A bstract A search for diphoton resonances in the mass range between 10 and 70 GeV with the ATLAS experiment at the Large Hadron Collider (LHC) is presented. The analysis is based on pp collision data corresponding to an integrated luminosity of 138 fb − 1 at a centre-of-mass energy of 13 TeV recorded from 2015 to 2018. Previous searches for diphot...

A bstract This paper describes a search for dark photons ( γ d ) in proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV at the Large Hadron Collider (LHC). The dark photons are searched for in the decay of Higgs bosons ( H → γγ d ) produced through the ZH production mode. The transverse mass of the system, made of the photon and the missing trans...

A bstract Differential and double-differential distributions of kinematic variables of leptons from decays of top-quark pairs ( $$ t\overline{t} $$ t t ¯ ) 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 $$ \sqrt{s} $$ s = 13 TeV and correspond to an integrated...

A bstract A search for high-mass charged and neutral bosons decaying to Wγ and Zγ final states is presented in this paper. The analysis uses a data sample of $$ \sqrt{s} $$ s = 13 TeV proton-proton collisions with an integrated luminosity of 139 fb − 1 collected by the ATLAS detector during LHC Run 2 operation. The sensitivity of the search is dete...

A bstract A search for vector-like leptons in multilepton (two, three, or four-or-more electrons plus muons) final states with zero or more hadronic τ -lepton decays is presented. The search is performed using a dataset corresponding to an integrated luminosity of 139 fb − 1 of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded...

A bstract Several extensions of the Standard Model predict the production of dark matter particles at the LHC. A search for dark matter particles produced in association with a dark Higgs boson decaying into W ⁺ W − in the $$ {\ell}^{\pm}\nu q{\overline{q}}^{\prime }, $$ ℓ ± νq q ¯ ′ , final states with ℓ = e, μ is presented. This analysis uses 139...