We extend the results of Lappi et al. [<a href="http://dx.doi.org/10.1140/epjc/s10052-023-12365-2">Eur. Phys. J. C 84, 84 (2024)</a>] to show that it is possible to obtain expressions for the longitudinal, singlet, and gluon structure functions <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>F</mi><mi>L</mi></msub></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>F</mi><mi>S</mi></msub></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>G</mi></math> in deep inelastic scattering directly in terms of the measured functions <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>F</mi><mn>2</mn></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi><msub><mi>F</mi><mn>2</mn></msub><mo>/</mo><mi>ln</mi><mo stretchy="false">(</mo><msup><mi>Q</mi><mn>2</mn></msup><mo stretchy="false">)</mo></math> modulo nonsinglet corrections expected to be small at very small <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math>. The latter can be treated at low <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math> using existing quark distributions. Our results are presented consistently to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>O</mi><mo stretchy="false">(</mo><msubsup><mi>α</mi><mi>s</mi><mn>2</mn></msubsup><mo stretchy="false">)</mo></math>, correcting and extending the mixed-order results of Lappi et al..

Iran

G.R. Boroun

United States

Loyal Durand

Phuoc Ha

Direct determination of the structure functions <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>F</mi><mi>L</mi></msub></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>F</mi><mi>S</mi></msub></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>G</mi></math> from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>F</mi><mn>2</mn></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi><msub><mi>F</mi><mn>2</mn></msub><mo>/</mo><mi>d</mi><msup><mi>Q</mi><mn>2</mn></msup></math> to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>O</mi><mo stretchy="false">(</mo><msubsup><mi>α</mi><mi>s</mi><mn>2</mn></msubsup><mo stretchy="false">)</mo></math>

This Letter reports on the first evidence of inclusive Higgs-boson production at high transverse momentum in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>b</mi><mover accent="true"><mrow><mi>b</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover></mrow></math> final state, reconstructed in a single large-radius jet. The results are based on proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider at a center-of-mass energies of 13 and 13.6 TeV, corresponding to a total integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>301</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>. The study profits from the large background suppression provided by the use of a new transformer-based algorithm for jet identification and the sharper mass and transverse momentum, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi mathvariant="normal">T</mi></msub></math>, resolution from a dedicated regression model. The yield relative to the standard model prediction for Higgs bosons produced at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi mathvariant="normal">T</mi></msub></math> larger than 450 GeV is measured to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1.53</mn><mo>±</mo><mn>0.2</mn><msubsup><mrow><mn>7</mn><mo stretchy="false">)</mo></mrow><mrow><mo>−</mo><mn>0.27</mn></mrow><mrow><mo>+</mo><mn>0.33</mn></mrow></msubsup><mrow><mo>±</mo></mrow><mn>0.17</mn></mrow></math>, where the first uncertainty is statistical, the second is experimental systematic, and the third accounts for theory systematic, corresponding to an observed (expected) significance of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3.8</mn><mi>σ</mi><mo stretchy="false">(</mo><mn>2.5</mn><mi>σ</mi><mo stretchy="false">)</mo></math> relative to the background-only hypothesis. Results are also obtained in three Higgs boson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi mathvariant="normal">T</mi></msub></math> intervals and found to be compatible with standard model predictions, where the first uncertainty is statistical, the second is experimental systematic, and the third accounts for theory systematic.

France

G. Aad

Norway

E. Aakvaag

B. Abbott

United Arab Emirates

S. Abdelhameed

Germany

K. Abeling

N.J. Abicht

S.H. Abidi

M. Aboelela

Morocco

A. Aboulhorma

Israel

H. Abramowicz

Italy

B.S. Acharya

A. Ackermann

C. Adam Bourdarios

Poland

L. Adamczyk

S.V. Addepalli

United Kingdom

M.J. Addison

J. Adelman

Türkiye

A. Adiguzel

T. Adye

A.A. Affolder

Y. Afik

Spain

M.N. Agaras

A. Aggarwal

Romania

C. Agheorghiesei

A. Ahmad

F. Ahmadov

S. Ahuja

China

X. Ai

G. Aielli

A. Aikot

M. Ait Tamlihat

Sweden

T.P.A. Åkesson

Japan

D. Akiyama

N.N. Akolkar

S. Aktas

G.L. Alberghi

Canada

J. Albert

Switzerland

U. Alberti

P. Albicocco

S. Alderweireldt

Z.L. Alegria

CERN

M. Aleksa

I.N. Aleksandrov

C. Alexa

Greece

T. Alexopoulos

F. Alfonsi

M. Algren

M. Alhroob

Czechia

B. Ali

H.M.J. Ali

S. Ali

S.W. Alibocus

South Africa

M. Aliev

G. Alimonti

C. Allaire

B.M.M. Allbrooke

D.R. Allen

J.S. Allen

J.F. Allen

Australia

C.S. Alley

E.R. Almazan

A. Aloisio

Argentina

F. Alonso

C. Alpigiani

A. Alvarez Fernandez

M. Alves Cardoso

M.G. Alviggi

M. Aly

Brazil

Y. Amaral Coutinho

C. Amelung

M. Amerl

T. Amezza

B. Amini

K. Amirie

A. Amirkhanov

D. Amperiadou

S. An

C. Anastopoulos

T. Andeen

J.K. Anders

A.C. Anderson

A. Andreazza

S. Angelidakis

A. Angerami

A.V. Anisenkov

A. Annovi

C. Antel

E. Antipov

M. Antonelli

F. Anulli

M. Aoki

T. Aoki

M.A. Aparo

L. Aperio Bella

M. Apicella

C. Appelt

A. Apyan

M. Arampatzi

S.J. Arbiol Val

Evidence of Higgs Boson Inclusive Production at High Transverse Momentum Decaying to a Pair of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi></math>-Quarks with the ATLAS Detector

A measurement of correction factors for the hadronic jet energy scale and resolution in the ATLAS detector is presented. These correction factors account for differences between simulated and observed data. They are obtained by analysing a selection of top quark events collected in proton–proton collisions by ATLAS between the years 2015 and 2018 at a centre-of-mass energy $$\sqrt{s} = 13$$ $$\text {T{eV}}$$ as well as in 2022 and 2023 at $$\sqrt{s} = 13.6$$ $$\text {T{eV}}$$ . The impact of different jet energy scale or resolution corrections on the reconstructed mass of the hadronically decaying $\textit{W}$ boson from top-quark decays in simulation is quantified. The correction factors are extracted from a fit to the parameterised reconstructed $\textit{W}$-boson mass distribution to data. The energy scale and resolution corrections are measured as a function of the jet transverse momentum between 20 and 200 GeV and absolute pseudorapidity less than 0.8. The uncertainties in the energy scale range from about 0.93% to about 1.7% for jets between 35 and 200 $$\text {G{eV}}$$ , while for the energy resolution the uncertainties range from about 14 to 28%. The method presented will be used in conjunction with other techniques to further improve ATLAS jet energy scale and resolution precision.

N. Abicht

S. Abidi

B. Acharya

C. Bourdarios

S. Addepalli

M. Addison

A. Affolder

M. Agaras

Azerbaijan

M. Tamlihat

B. Aitbenchikh

T. Åkesson

N. Akolkar

G. Alberghi

G. Albouy

Z. Alegria

I. Aleksandrov

Saudi Arabia

H. Ali

S. Alibocus

W. Alkakhi

B. Allbrooke

D. Allen

J. Allen

C. Alley

Z. Alsolami

A. Fernandez

M. Cardoso

M. Alviggi

Y. Coutinho

A. Ambler

Portugal

S. Santos

J. Anders

A. Anderson

A. Anisenkov

M. Aparo

L. Bella

Calibration of the jet energy scale and resolution of small-radius jets using semileptonic $$t\bar{t}$$ events with the ATLAS detector

This paper presents the first search for non-resonant Higgs boson pair production in association with a top-quark pair ( $$ t\overline{t} HH $$ ) using proton–proton collision data collected with the ATLAS detector at the Large Hadron Collider. The data sample corresponds to an integrated luminosity of 196 fb , comprising 140 fb at a centre-of-mass energy of $$ \sqrt{s}=13 $$ TeV and 56 fb at 13.6 TeV. The search targets three distinct final states expected from $$ t\overline{t} HH $$ decays: (i) one lepton (electron or muon) with at least five $\textit{b}$-quarks, (ii) at least two $\textit{b}$-quarks accompanied by two leptons with the same electric charges or multiple leptons, and (iii) at least three $\textit{b}$-quarks with two photons. The $$ t\overline{t} HH $$ production cross-section, relative to its Standard Model prediction, is measured to be $$ {\mu}_{t\overline{t} HH}=-{3}_{-12}^{+11} $$ . This result corresponds to a 95% confidence-level upper limit of 20 times the Standard Model prediction for the $$ t\overline{t} HH $$ production cross-section, with an expected limit of 21. The Higgs effective field theory Wilson coefficient $$ {c}_{t\overline{t} HH} $$ is also constrained at the same confidence level to the range of $$ -3.9&lt;{c}_{t\overline{t} HH}&lt;3.3 $$ , compared with the expected range of $$ -4.0&lt;{c}_{t\overline{t} HH}&lt;3.5 $$ .

E. Almazan

Search for Higgs boson pair production in association with top-quark pairs using 196 fb $\textit{−}$1 of proton–proton collision data at $$ \sqrt{s}=13 $$ and 13.6 TeV with the ATLAS detector

A search for long-lived particles in events with significant missing transverse momentum and at least one displaced vertex is presented. This analysis is performed using 137 fb of $\textit{pp}$ collision data collected between 2016–2018 during Run 2 of the Large Hadron Collider by the ATLAS detector. Displaced vertices are identified using two different secondary vertexing algorithms, including a novel “fuzzy” vertexing algorithm optimized for identifying displaced decays of heavy quarks. Separate searches are performed using each algorithm, and the expected Standard Model background is independently estimated for each search using a data-driven procedure. No significant excess is observed over the background in either case. The results are used to set 95% confidence-level limits on potential beyond-the-Standard Model physics that could produce this final state. Results are interpreted in the context of four models: long-lived gluinos that form $\textit{R}$-hadrons before decaying, neutralinos decaying via Higgs-mediated channels in the Bino-Wino coannihilation model, long-lived Higgsinos decaying to axinos, and an exotic Higgs portal model predicting displaced decays of light pseudoscalars.

Search for displaced decays of long-lived particles in events with missing transverse momentum in $$ \sqrt{s}=13 $$ TeV $\textit{pp}$ collisions with the ATLAS detector

Wilson coefficients in dimension-six effective field theory are constrained in a combined fit to several ATLAS measurements. These inputs probe Higgs-boson processes across multiple production and decay modes, di-Higgs signatures in the $$ b\overline{b}\gamma \gamma $$ and $$ b\overline{b}\tau \tau $$ final states, $\textit{WW}$ and $\textit{WZ}$ diboson signatures, electroweak $\textit{Zjj}$ final states, high-mass Drell–Yan interactions, and $$ t\overline{t} $$ events in both resolved and boosted topologies. Precision electroweak observables from LEP, SLD, and ATLAS are also included. A total of 48 parameters, including individual Wilson coefficients in the Warsaw basis and linear combinations of Wilson coefficients, are constrained simultaneously. Constraints on two-Higgs-doublet models and heavy-vector-boson models are also obtained by matching a relevant sub-set of the results with their parameters. This combined fit provides the most comprehensive effective field theory interpretation of experimental data by the ATLAS Collaboration to date. No significant deviations from the Standard Model are observed.

S. Arbiol Val

Effective field theory interpretation of ATLAS measurements involving the Higgs boson, electroweak bosons and the top quark

A search is conducted in proton–proton collisions at the Large Hadron Collider for photon-induced production $\textit{pp}$ → $\textit{pp}$ + $\textit{γγ,}$ ($\textit{γγ}$ → $\textit{VX}$) of a visible particle $\textit{V}$ decaying into a pair of same-flavour charged leptons ($\textit{e}$ $\textit{e}$ or $\textit{μ}$ $\textit{μ}$ ) and an undetected invisible component $\textit{X}$. Measurements of the outgoing proton energies by the ATLAS forward proton spectrometer allow the full photon–photon four-momentum to be reconstructed. By subtracting the visible four-momentum of the central system measured with the ATLAS detector, the “missing mass” of any event components not detected in the central region can be reconstructed, enabling the reconstruction of $\textit{X}$ without knowing its properties, thus allowing the search to be model-independent. A search for a narrow resonance is performed in the missing-mass spectrum between 100 GeV and 900 GeV. The analysis uses data collected in 2017 from proton–proton collisions at a centre-of-mass energy of $$ \sqrt{s}=13 $$ TeV, corresponding to an integrated luminosity of 14.7 fb . No significant excess over the Standard Model expectation is observed and upper limits at 95% confidence level are set on the fiducial cross sections for three different signal models in the range between 128 and 2.5 fb. Additionally, model-independent limits are set on the visible cross section of BSM processes, for two sets of selection criteria. Both individual lepton flavour decay channels of the visible boson and a combination of the two channels are considered.

S. Amor Dos Santos

Missing-mass search in forward-proton-tagged dilepton events with the ATLAS detector

This paper reports a search for decays of long-lived charginos or $\textit{τ}$-sleptons to final states containing a short disappearing track, a single high-energy jet, and missing transverse momentum. The search uses 137 fb of data from 13 TeV proton–proton collisions recorded by the ATLAS detector during Run 2 of the LHC. Multiple search regions are defined, all requiring the presence of a track reconstructed from either three or four measurements in the innermost layers of the ATLAS detector. Regions with tracks having only three measurements are further characterised by the absence or presence of a low-energy charged pion reconstructed using a dedicated algorithm, leveraging machine learning. Data-driven methods are used to estimate the background contributions in the search regions. No significant excesses are found and 95% CL lower limits are placed on the masses of charginos and $\textit{τ}$-sleptons in the lifetime range 0.01–10 ns. Observed (expected) mass limits of up to 225 GeV (250 GeV) are set for pure-higgsino charginos in scenarios with lifetimes below 0.03 ns, where the electroweakino mass splitting is entirely due to loop corrections involving the Standard Model bosons, and up to 720 GeV (840 GeV) for charginos with a lifetime of around 1 ns. For wino production, charginos with masses up to 880 GeV (1020 GeV) are excluded for lifetimes of around 1 ns. For $\textit{τ}$-sleptons with lifetimes of around 1 ns, masses are excluded up to 320 GeV (390 GeV) in Constrained Minimal Supersymmetric Standard Model scenarios and 300 GeV (380 GeV) in Gauge-Mediated Supersymmetry-Breaking scenarios.

Search for long-lived charginos and $\textit{τ}$-sleptons using final states with a disappearing track in $\textit{pp}$ collisions at $$ \sqrt{s}=13 $$ TeV with the ATLAS detector

A search for charged lepton flavour violation in <italic>&#964;</italic>&#8239;&#8594;&#8239;3 <italic>&#956;</italic> decays is performed in <italic>pp</italic> collisions at a centre-of-mass energy of 13 TeV using ATLAS data collected between 2016 and 2018, corresponding to an integrated luminosity of 137 <math altimg='si27.svg'><msup><mtext>fb</mtext><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></math>. The search is optimised for the electroweak <italic>W</italic>&#8239;&#8594;&#8239; <italic>&#964;&#957;</italic> production channel, due to its higher trigger efficiency, but also considers potential signal events from heavy-flavour production. Data are collected using two-muon and three-muon triggers and a multivariate analysis is used to separate the signal from the background. An unbinned likelihood fit is then performed to the resulting three-muon invariant mass spectrum and the data are found to be compatible with the background-only hypothesis. The observed (expected) limit on the branching ratio <italic>B</italic>( <italic>&#964;</italic>&#8239;&#8594;&#8239;3 <italic>&#956;</italic>) is found to be <math altimg='si28.svg'><mrow><mn>8.7</mn><mo linebreak='goodbreak'>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>8</mn></mrow></msup></mrow></math> ( <math altimg='si29.svg'><mrow><mn>7.5</mn><mo linebreak='goodbreak'>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>8</mn></mrow></msup></mrow></math>) at 90% CL

A search for lepton-flavour violating <italic>&#964;</italic>&#8239;&#8594;&#8239;3 <italic>&#956;</italic> decays with the ATLAS detector

A search is presented for emerging jets using $$140~\textrm{fb}^{-1}$$ of proton–proton collision data at $$\sqrt{s} = 13~\textrm{TeV}$$ , collected by the ATLAS experiment between 2015 and 2018. The search looks for the existence of a dark sector with symmetries similar to those in quantum chromodynamics. This dark sector is populated with dark quarks, which undergo showering similar to quarks in the Standard Model, leading to a high multiplicity of long-lived dark hadrons within a dark jet. These dark hadrons subsequently decay to Standard Model particles via a new heavy scalar mediating particle $$\phi $$ . This results in jets which contain multiple displaced vertices, known as emerging jets. This analysis targets four-jet topologies, with two emerging jets and two Standard Model jets, resulting from the decay of pair-produced scalar mediators. No significant excess above the Standard Model background is observed. For dark pion proper decay lengths of $$20~\textrm{mm}$$ , mediator masses are excluded between 1 and $$2~\textrm{TeV}$$ assuming a dark pion mass of $$20~\textrm{GeV}$$ .

Y. Abulaiti

A. Akimov

P. Allport

C. Ames

D. Amidei

K. Amos

Search for emerging jets in $\textit{pp}$ collisions at $$\sqrt{s} = 13~\textrm{TeV}$$ with the ATLAS experiment