The angular distributions of Drell–Yan lepton pairs provide sensitive probes of the underlying dynamics of quantum chromodynamics (QCD) effects in vector-boson production. This paper presents for the first time the measurement of the full set of angular coefficients together with the differential cross-section as a function of the transverse momentum of the $\textit{W}$ boson, in the full phase space of the decay leptons. The measurements are performed separately for the $$W^-$$ and $$W^+$$ channels. The analysis uses proton–proton collision data recorded by the ATLAS experiment at the Large Hadron Collider in 2017 and 2018, during special low-luminosity runs with a reduced number of interactions per bunch crossings (pile-up). The data correspond to an integrated luminosity of 338 pb $$^{-1}$$ at a centre-of-mass energy of $$\sqrt{s} = 13$$ TeV. The low pile-up environment provides excellent experimental conditions for high-precision measurements of $\textit{W}$-boson production. All results agree with theoretical predictions incorporating finite-order QCD corrections up to order $$\alpha _S^2$$ .

France

G. Aad

Norway

E. Aakvaag

United States

B. Abbott

United Arab Emirates

S. Abdelhameed

Germany

K. Abeling

N. Abicht

S. Abidi

M. Aboelela

Morocco

A. Aboulhorma

Israel

H. Abramowicz

Y. Abulaiti

Italy

United Kingdom

B. Acharya

A. Ackermann

C. Bourdarios

Poland

L. Adamczyk

S. Addepalli

M. Addison

J. Adelman

Türkiye

A. Adiguzel

T. Adye

A. Affolder

Y. Afik

Spain

M. Agaras

A. Aggarwal

Romania

C. Agheorghiesei

Azerbaijan

F. Ahmadov

S. Ahuja

China

X. Ai

G. Aielli

A. Aikot

M. Tamlihat

B. Aitbenchikh

M. Akbiyik

Sweden

T. Åkesson

A. Akimov

Japan

D. Akiyama

N. Akolkar

S. Aktas

G. Alberghi

Canada

J. Albert

Switzerland

U. Alberti

P. Albicocco

G. Albouy

S. Alderweireldt

Z. Alegria

M. Aleksa

I. Aleksandrov

C. Alexa

Greece

T. Alexopoulos

F. Alfonsi

M. Algren

M. Alhroob

Czechia

B. Ali

Saudi Arabia

H. Ali

S. Ali

S. Alibocus

South Africa

M. Aliev

G. Alimonti

W. Alkakhi

C. Allaire

B. Allbrooke

D. Allen

J. Allen

P. Allport

A. Aloisio

Argentina

F. Alonso

C. Alpigiani

Z. Alsolami

A. Fernandez

M. Cardoso

M. Alviggi

M. Aly

Brazil

Y. Coutinho

A. Ambler

C. Amelung

M. Amerl

C. Ames

T. Amezza

D. Amidei

B. Amini

K. Amirie

A. Amirkhanov

Portugal

S. Santos

K. Amos

D. Amperiadou

S. An

C. Anastopoulos

T. Andeen

J. Anders

A. Anderson

A. Andreazza

S. Angelidakis

A. Angerami

A. Anisenkov

A. Annovi

C. Antel

E. Antipov

M. Antonelli

Measurement of the $\textit{W}$-boson angular coefficients and transverse momentum in $$p\!p$$ collisions at $$\sqrt{s}=13$$ TeV with the ATLAS detector

The inclusive top quark pair ( $$t\bar{t}$$ ) cross-section $$\sigma _{t\bar{t}}$$ has been measured in proton–proton collisions at $$\sqrt{s}=13\,\text {TeV}$$ , using $$140\,{\text {fb}^{-1}} $$ of data collected by the ATLAS experiment at the Large Hadron Collider. Using events with an opposite-charge $$e\mu $$ pair and $\textit{b}$-tagged jets, the cross-section is measured to be: where the uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, the integrated luminosity, and the proton beam energy, giving a total uncertainty of 1.3%. The result is used to determine the top quark pole mass via the dependence of the predicted cross-section on $${m_{t}^\textrm{pole}}$$ , giving $${m_{t}^\textrm{pole}}=172.8^{+1.5}_{-1.7}$$ $$\text {GeV}$$ . The same event sample is used to measure absolute and normalised differential cross-sections for the $$t\bar{t} \rightarrow e\mu \nu \bar{\nu }b\bar{b} $$ process as a function of single-lepton and dilepton kinematic variables. Complementary measurements of $$e\mu b\bar{b} $$ production, treating both $$t\bar{t}$$ and $\textit{Wt}$ events as signal, are also provided. Both sets of differential cross-sections are compared to the predictions of various Monte Carlo event generators, demonstrating that the state-of-the-art generators and $\textit{bb}$4$\textit{l}$ describe the data better than .

C. Adam Bourdarios

A. Alvarez Fernandez

M. Alves Cardoso

Y. Amaral Coutinho

S. Amor Dos Santos

F. Anulli

Precise measurement of the $$t\bar{t}$$ production cross-section and lepton differential distributions in $$ e\mu $$ dilepton events from $$\sqrt{s}=13\,\text {TeV}$$ $\textit{pp}$ collisions with the ATLAS detector

This Letter analyzes the sensitivity of event geometry estimators to the initial-state kinematics of hard scattering in proton–lead collisions. This analysis uses dijets as a proxy for the parton–parton scattering configuration, correlating it with event geometry estimators, namely the energy deposited in the Zero-Degree Calorimeter and the transverse energy recorded in the Forward Calorimeter in the Pb-going direction. The analysis uses data recorded by the ATLAS detector at the Large Hadron Collider with a nucleon–nucleon center-of-mass energy of 8.16 TeV, corresponding to an integrated luminosity of 56 nb <math altimg='si6.svg'><msup><mrow /><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></math>. The jets are measured within the pseudorapidity interval &#8722;2.8 &#8239;&lt;&#8239; <italic>&#951;</italic> &#8239;&lt;&#8239; 4.5, where positive <italic>&#951;</italic> values correspond to the direction of the proton beam. Results are presented as a function of the Bjorken- <italic>x</italic> of the parton originating from the proton, <italic>x<inf>p</inf></italic>. Both event geometry estimators are found to be dependent on <italic>x<inf>p</inf></italic>, with the energy deposited in the Zero-Degree Calorimeter about six times less sensitive to <italic>x<inf>p</inf></italic> compared with the transverse energy deposited in the Forward Calorimeter.

N.J. Abicht

S.H. Abidi

B.S. Acharya

S.V. Addepalli

M.J. Addison

A.A. Affolder

M.N. Agaras

M. Ait Tamlihat

T.P.A. Åkesson

A.V. Akimov

N.N. Akolkar

G.L. Alberghi

G.L. Albouy

Z.L. Alegria

I.N. Aleksandrov

H.M.J. Ali

S.W. Alibocus

B.M.M. Allbrooke

J.S. Allen

J.F. Allen

P.P. Allport

Z.M.K. Alsolami

M.G. Alviggi

C.G. Ames

S.P. Amor Dos Santos

K.R. Amos

J.K. Anders

A.C. Anderson

A.V. Anisenkov

M. Aoki

T. Aoki

Characterization of nuclear breakup as a function of hard-scattering kinematics using dijets measured by ATLAS in <italic>p</italic>+Pb collisions

A search for final states characterised by at least one isolated high transverse-momentum photon, jets and large missing transverse momentum is presented. Such a final state might occur in gauge-mediated supersymmetric models where a pair of binos and higgsinos mix to form neutralinos, one of which decays into a photon plus a gravitino while the other decays into a Higgs boson, a $\textit{Z}$ boson or a photon, plus a gravitino. The search is performed using the full Run-2 data sample of 140 fb of $$ \sqrt{s}=13 $$ TeV proton-proton collisions collected by the ATLAS detector at the Large Hadron Collider. No significant excess of events is observed above the Standard Model prediction and model-dependent exclusion limits at the 95% confidence level are set. These limits are interpreted in terms of the masses of gauginos, which are excluded up to 1.2 TeV depending on their branching ratios, and on their branching ratios as a function of their mass.

Search for signatures of electroweakinos with photons, jets, and large missing transverse momentum in $$ \sqrt{s}=13 $$ TeV $\textit{pp}$ collisions with the ATLAS detector

The top-quark mass is measured using top-quark decays producing an isolated lepton and $\textit{J}$/$\textit{ψ}$ meson reconstructed in its $\textit{μ}$ $\textit{μ}$ decay mode. The data sample was recorded with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of $$ \sqrt{s}=13 $$ TeV during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb . The measurement is based on the invariant mass $\textit{m}$($\textit{ℓμ}$ $\textit{μ}$ ) of the system made of the isolated lepton $\textit{ℓ}$ from the $\textit{W}$ boson decay and the non-isolated $\textit{μ}$ $\textit{μ}$ pair from a $\textit{J}$/$\textit{ψ}$ decay of a $\textit{b}$-hadron, exploiting its sensitivity to the top-quark mass. An unbinned maximum-likelihood fit to the $\textit{m}$($\textit{ℓμ}$ $\textit{μ}$ ) distribution is performed to extract the top-quark mass. The top-quark mass is measured to be $\textit{m}$ = 172.17 ± 0.80 (stat) ± 0.81 (syst) ± 1.07 (recoil) GeV, with a total uncertainty of 1.56 GeV. The third uncertainty arises from changing the dipole parton shower gluon-recoil scheme used in top-quark decays.

Measurement of the top-quark mass using decays with a $\textit{J/ψ}$ meson at $$ \sqrt{s}=13 $$ TeV with the ATLAS detector

A search for the resonant production of a heavy scalar <italic>X</italic> decaying into a lighter scalar <italic>S</italic> and a Higgs boson, through the process <math altimg='si13.svg'><mrow><mi>X</mi><mo>&#8594;</mo><mi>S</mi><mrow><mo>(</mo><mo>&#8594;</mo><mi>b</mi><mover accent='true'><mi>b</mi><mo>&#175;</mo></mover><mo>)</mo></mrow><mi>H</mi><mrow><mo>(</mo><mo>&#8594;</mo><mi>&#947;</mi><mi>&#947;</mi><mo>)</mo></mrow></mrow></math>, where the two photons are consistent with the Higgs boson decay, is performed. The search is conducted using integrated luminosities of 140 and 59 fb <math altimg='si11.svg'><msup><mrow /><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></math> of proton&#8211;proton collision data at centre-of-mass energies of 13 and 13.6 TeV, respectively, recorded with the ATLAS detector at the LHC. The search is performed over the mass ranges of 170 &#8239;&#8804;&#8239; <italic>m<inf>X</inf></italic> &#8239;&#8804;&#8239; 1000 GeV and 15 &#8239;&#8804;&#8239; <italic>m<inf>S</inf></italic> &#8239;&#8804;&#8239; 500 GeV. No significant excess over the Standard Model background predictions is observed and limits at 95% confidence level are set on the product of cross section and branching fraction for the process <math altimg='si13.svg'><mrow><mi>X</mi><mo>&#8594;</mo><mi>S</mi><mrow><mo>(</mo><mo>&#8594;</mo><mi>b</mi><mover accent='true'><mi>b</mi><mo>&#175;</mo></mover><mo>)</mo></mrow><mi>H</mi><mrow><mo>(</mo><mo>&#8594;</mo><mi>&#947;</mi><mi>&#947;</mi><mo>)</mo></mrow></mrow></math> at 13 TeV, ranging from 9 fb to 0.06 fb.

Search for a resonance decaying into a scalar particle and a Higgs boson in the final state with two bottom quarks and two photons with 199 fb <math altimg='si11.svg'><msup><mrow /><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></math> of data collected at <math altimg='si12.svg'><msqrt><mi>s</mi></msqrt></math>=13 and 13.6 TeV with the ATLAS detector

The ATLAS experiment has performed a measurement of coherent exclusive $\textit{J/ψ}$ → $\textit{μ}$ $\textit{μ}$ production in ultraperipheral Pb+Pb collisions at $$ \sqrt{s_{\textrm{NN}}}=5.36 $$ TeV. The data was recorded at the Large Hadron Collider (LHC) during 2023, and corresponds to an integrated luminosity of 79 $\textit{μ}$b . Exclusive $\textit{J/ψ}$ candidates were selected with a dedicated track-sensitive trigger based on the ATLAS transition radiation tracker. The analysis involves reconstruction of the dimuon invariant mass based on muon tracks from the inner detector, as the muon transverse momentum range of interest precludes the use of the standard muon reconstruction and identification algorithms. Differential cross sections are measured as a function of $\textit{J/ψ}$ rapidity and are compared with theoretical predictions. After extrapolation to $$ \sqrt{s_{\textrm{NN}}}=5.02 $$ TeV, they are also compared with previous measurements performed by other experiments using data from LHC Run 2. While the results agree reasonably well with theoretical predictions, they are in tension with previous Run-2 results for the central rapidity region.

Measurement of coherent exclusive $\textit{J/ψ → μ}$ + $\textit{μ}$ $\textit{−}$ production in ultraperipheral Pb+Pb collisions at $$ \sqrt{s_{\textrm{NN}}}=5.36 $$ TeV with the ATLAS detector

Erratum: The environmental impact, carbon emissions and sustainability of computing in the ATLAS experiment

A search for the Higgs boson decay to a <italic>Z</italic> boson and a photon in the &#8467;&#8467; <italic>&#947;</italic> ( <math altimg='si38.svg'><mrow><mi>&#8467;</mi><mo linebreak='goodbreak'>=</mo><mi>e</mi><mo>,</mo><mi>&#956;</mi></mrow></math>) final state is performed using <italic>pp</italic> collisions at <math altimg='si39.svg'><mrow><msqrt><mi>s</mi></msqrt><mo linebreak='goodbreak'>=</mo><mn>13.6</mn></mrow></math> TeV recorded with the ATLAS detector at the Large Hadron Collider during 2022&#8211;2024, corresponding to an integrated luminosity of 165 fb <math altimg='si40.svg'><msup><mrow /><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></math>. The signal yield, normalised to the Standard Model prediction, is measured to be <math altimg='si41.svg'><mrow><mi>&#956;</mi><mo linebreak='goodbreak'>=</mo><mn>0</mn><mo>.</mo><msubsup><mn>9</mn><mrow><mo>&#8722;</mo><mn>0.6</mn></mrow><mrow><mo>+</mo><mn>0.7</mn></mrow></msubsup></mrow></math>, compatible with the expected value of <math altimg='si42.svg'><mrow><mi>&#956;</mi><mo linebreak='goodbreak'>=</mo><mn>1.0</mn><mo>&#177;</mo><mn>0.7</mn></mrow></math>. This corresponds to an observed (expected) signal significance of 1.4 (1.5) standard deviations under the background-only hypothesis. This result is combined with that of a similar search performed with 140 fb <math altimg='si40.svg'><msup><mrow /><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></math> of <math altimg='si37.svg'><mrow><msqrt><mi>s</mi></msqrt><mo linebreak='goodbreak'>=</mo><mn>13</mn></mrow></math> TeV <italic>pp</italic> collisions to provide the best expected sensitivity to date to this rare decay, namely an observed (expected) signal strength of <math altimg='si43.svg'><mrow><mi>&#956;</mi><mo linebreak='goodbreak'>=</mo><mn>1</mn><mo>.</mo><msubsup><mn>3</mn><mrow><mo>&#8722;</mo><mn>0.5</mn></mrow><mrow><mo>+</mo><mn>0.6</mn></mrow></msubsup></mrow></math> ( <math altimg='si44.svg'><mrow><mi>&#956;</mi><mo linebreak='goodbreak'>=</mo><mn>1</mn><mo>.</mo><msubsup><mn>0</mn><mrow><mo>&#8722;</mo><mn>0.5</mn></mrow><mrow><mo>+</mo><mn>0.6</mn></mrow></msubsup></mrow></math>), corresponding to an observed (expected) significance of 2.5 (1.9) standard deviations. The measurement is consistent with the Standard Model expectation.

Search for the Higgs boson decay to a <italic>Z</italic> boson and a photon in <italic>pp</italic> collisions at <math altimg='si37.svg'><mrow><msqrt><mi>s</mi></msqrt><mo linebreak='goodbreak'>=</mo><mn>13</mn></mrow></math> TeV and 13.6 TeV with the ATLAS detector

A model-agnostic search for Beyond the Standard Model physics is presented, targeting final states with at least four light leptons (electrons or muons). The search regions are separated by event topology and unsupervised machine learning is used to identify anomalous events in the full 140 fb $$^{-1}$$ of proton–proton collision data collected with the ATLAS detector during Run 2. No significant excess above the Standard Model background expectation is observed. Model-agnostic limits are presented in each topology, along with limits on several benchmark models including vector-like leptons, wino-like charginos and neutralinos, or smuons. Limits are set on the flavourful vector-like lepton model for the first time.

Search for Beyond the Standard Model physics with anomaly detection in multilepton final states in $\textit{pp}$ collisions at $$\sqrt{s}=13~\textrm{TeV}$$ with the ATLAS detector