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  1. A search for the nonresonant production of Higgs boson pairs in theHHbb¯τ+τchannel is performed using140fb1of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The analysis strategy is optimized to probe anomalous values of the Higgs boson self-coupling modifierκλand of the quarticHHVV(V=W,Z) coupling modifierκ2V. No significant excess above the expected background from Standard Model processes is observed. An observed (expected) upper limitμHH<5.9(3.3)is set at 95% confidence-level on the Higgs boson pair production cross section normalized to its Standard Model prediction. The coupling modifiers are constrained to an observed (expected) 95% confidence interval of3.1<κλ<9.0(2.5<κλ<9.3) and0.5<κ2V<2.7(0.2<κ2V<2.4), assuming all other Higgs boson couplings are fixed to the Standard Model prediction. The results are also interpreted in the context of effective field theories via constraints on anomalous Higgs boson couplings and Higgs boson pair production cross sections assuming different kinematic benchmark scenarios.

    © 2024 CERN, for the ATLAS Collaboration2024CERN 
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    Free, publicly-accessible full text available August 1, 2025
  2. Abstract

    A search for leptoquark pair production decaying into$$te^- \bar{t}e^+$$te-t¯e+or$$t\mu ^- \bar{t}\mu ^+$$tμ-t¯μ+in final states with multiple leptons is presented. The search is based on a dataset ofppcollisions at$$\sqrt{s}=13~\text {TeV} $$s=13TeVrecorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb$$^{-1}$$-1. Four signal regions, with the requirement of at least three light leptons (electron or muon) and at least two jets out of which at least one jet is identified as coming from ab-hadron, are considered based on the number of leptons of a given flavour. The main background processes are estimated using dedicated control regions in a simultaneous fit with the signal regions to data. No excess above the Standard Model background prediction is observed and 95% confidence level limits on the production cross section times branching ratio are derived as a function of the leptoquark mass. Under the assumption of exclusive decays into$$te^{-}$$te-($$t\mu ^{-}$$tμ-), the corresponding lower limit on the scalar mixed-generation leptoquark mass$$m_{\textrm{LQ}_{\textrm{mix}}^{\textrm{d}}}$$mLQmixdis at 1.58 (1.59) TeV and on the vector leptoquark mass$$m_{{\tilde{U}}_1}$$mU~1at 1.67 (1.67) TeV in the minimal coupling scenario and at 1.95 (1.95) TeV in the Yang–Mills scenario.

     
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    Free, publicly-accessible full text available August 1, 2025
  3. A search for high-mass resonances decaying into aτ-lepton and a neutrino using proton-proton collisions at a center-of-mass energy ofs=13TeVis presented. The full run 2 data sample corresponding to an integrated luminosity of139fb1recorded by the ATLAS experiment in the years 2015–2018 is analyzed. Theτ-lepton is reconstructed in its hadronic decay modes and the total transverse momentum carried out by neutrinos is inferred from the reconstructed missing transverse momentum. The search for new physics is performed on the transverse mass between theτ-lepton and the missing transverse momentum. No excess of events above the Standard Model expectation is observed and upper exclusion limits are set on theWτνproduction cross section. HeavyWvector bosons with masses up to 5.0 TeV are excluded at 95% confidence level, assuming that they have the same couplings as the Standard ModelWboson. For nonuniversal couplings,Wbosons are excluded for masses less than 3.5–5.0 TeV, depending on the model parameters. In addition, model-independent limits on the visible cross section times branching ratio are determined as a function of the lower threshold on the transverse mass of theτ-lepton and missing transverse momentum.

    <supplementary-material><permissions><copyright-statement>© 2024 CERN, for the ATLAS Collaboration</copyright-statement><copyright-year>2024</copyright-year><copyright-holder>CERN</copyright-holder></permissions></supplementary-material></sec> </div> <a href='#' class='show open-abstract' style='margin-left:10px;'>more »</a> <a href='#' class='hide close-abstract' style='margin-left:10px;'>« less</a> <div class="actions" style="padding-left:10px;"> <span class="reader-count"> Free, publicly-accessible full text available June 1, 2025</span> </div> </div><div class="clearfix"></div> </div> </li> <li> <div class="article item document" itemscope itemtype="http://schema.org/TechArticle"> <div class="item-info"> <div class="title"> <a href="https://par.nsf.gov/biblio/10534033-search-pair-production-higgsinos-events-two-higgs-bosons-missing-transverse-momentum-pp-collisions-atlas-experiment" itemprop="url"> <span class='span-link' itemprop="name">Search for pair production of higgsinos in events with two Higgs bosons and missing transverse momentum in s=13  TeV pp collisions at the ATLAS experiment</span> </a> </div> <div> <strong> <a class="misc external-link" href="https://doi.org/10.1103/PhysRevD.109.112011" target="_blank" title="Link to document DOI">https://doi.org/10.1103/PhysRevD.109.112011  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Aad, G</span> <span class="sep">; </span><span class="author" itemprop="author">Abbott, B</span> <span class="sep">; </span><span class="author" itemprop="author">Abeling, K</span> <span class="sep">; </span><span class="author" itemprop="author">Abicht, N J</span> <span class="sep">; </span><span class="author" itemprop="author">Abidi, S H</span> <span class="sep">; </span><span class="author" itemprop="author">Aboulhorma, A</span> <span class="sep">; </span><span class="author" itemprop="author">Abramowicz, H</span> <span class="sep">; </span><span class="author" itemprop="author">Abreu, H</span> <span class="sep">; </span><span class="author" itemprop="author">Abulaiti, Y</span> <span class="sep">; </span><span class="author" itemprop="author">Acharya, B S</span> <span class="sep">; </span><span class="author">et al</span></span> <span class="year">( <time itemprop="datePublished" datetime="2024-06-01">June 2024</time> , Physical Review D) </span> </div> <div style="cursor: pointer;-webkit-line-clamp: 5;" class="abstract" itemprop="description"> <p>This paper presents a search for pair production of higgsinos, the supersymmetric partners of the Higgs bosons, in scenarios with gauge-mediated supersymmetry breaking. Each higgsino is assumed to decay into a Higgs boson and a nearly massless gravitino. The search targets events where each Higgs boson decays into<math display='inline'><mi>b</mi><mover accent='true'><mi>b</mi><mo stretchy='false'>¯</mo></mover></math>, leading to a reconstructed final state with at least three energetic<math display='inline'><mi>b</mi></math>-jets and missing transverse momentum. Two complementary analysis channels are used, with each channel specifically targeting either low or high values of the higgsino mass. The low-mass (high-mass) channel exploits<math display='inline'><mrow><mn>126</mn><mtext> </mtext><mo stretchy='false'>(</mo><mn>139</mn><mo stretchy='false'>)</mo><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>of<math display='inline'><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>data collected by the ATLAS detector during Run 2 of the Large Hadron Collider. No significant excess above the Standard Model prediction is found. At 95% confidence level, masses between 130 GeV and 940 GeV are excluded for higgsinos decaying exclusively into Higgs bosons and gravitinos. Exclusion limits as a function of the higgsino decay branching ratio to a Higgs boson are also reported.</p> <sec><supplementary-material><permissions><copyright-statement>© 2024 CERN, for the ATLAS Collaboration</copyright-statement><copyright-year>2024</copyright-year><copyright-holder>CERN</copyright-holder></permissions></supplementary-material></sec> </div> <a href='#' class='show open-abstract' style='margin-left:10px;'>more »</a> <a href='#' class='hide close-abstract' style='margin-left:10px;'>« less</a> <div class="actions" style="padding-left:10px;"> <span class="reader-count"> Free, publicly-accessible full text available June 1, 2025</span> </div> </div><div class="clearfix"></div> </div> </li> <li> <div class="article item document" itemscope itemtype="http://schema.org/TechArticle"> <div class="item-info"> <div class="title"> <a href="https://par.nsf.gov/biblio/10508703-atlas-run-searches-electroweak-production-supersymmetric-particles-interpreted-within-pmssm" itemprop="url"> <span class='span-link' itemprop="name">ATLAS Run 2 searches for electroweak production of supersymmetric particles interpreted within the pMSSM</span> </a> </div> <div> <strong> <a class="misc external-link" href="https://doi.org/10.1007/JHEP05(2024)106" target="_blank" title="Link to document DOI">https://doi.org/10.1007/JHEP05(2024)106  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Aad, G</span> <span class="sep">; </span><span class="author" itemprop="author">Abbott, B</span> <span class="sep">; </span><span class="author" itemprop="author">Abeling, K</span> <span class="sep">; </span><span class="author" itemprop="author">Abicht, N J</span> <span class="sep">; </span><span class="author" itemprop="author">Abidi, S H</span> <span class="sep">; </span><span class="author" itemprop="author">Aboulhorma, A</span> <span class="sep">; </span><span class="author" itemprop="author">Abramowicz, H</span> <span class="sep">; </span><span class="author" itemprop="author">Abreu, H</span> <span class="sep">; </span><span class="author" itemprop="author">Abulaiti, Y</span> <span class="sep">; </span><span class="author" itemprop="author">Acharya, B S</span> <span class="sep">; </span><span class="author">et al</span></span> <span class="year">( <time itemprop="datePublished" datetime="2024-05-01">May 2024</time> , Journal of High Energy Physics) </span> </div> <div style="cursor: pointer;-webkit-line-clamp: 5;" class="abstract" itemprop="description"> <title>A<sc>bstract</sc>

    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 fb1of proton-proton data at a centre-of-mass energy of$$ \sqrt{s} $$s= 13 TeV collected at the Large Hadron Collider during its second data-taking run. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, whereR-parity conservation is assumed and the lightest supersymmetric particle is assumed to be the lightest neutralino. Constraints from previous electroweak, flavour and dark matter related measurements are also considered. The results are presented in terms of constraints on supersymmetric particle masses and are compared with limits from simplified models. Also shown is the impact of ATLAS searches on parameters such as the dark matter relic density and the spin-dependent and spin-independent scattering cross-sections targeted by direct dark matter detection experiments. The Higgs boson andZboson ‘funnel regions’, where a low-mass neutralino would not oversaturate the dark matter relic abundance, are almost completely excluded by the considered constraints. Example spectra for non-excluded supersymmetric models with light charginos and neutralinos are also presented.

     
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    Free, publicly-accessible full text available May 1, 2025
  4. A<sc>bstract</sc>

    A combination of searches for new heavy spin-1 resonances decaying into different pairings ofW,Z, or Higgs bosons, as well as directly into leptons or quarks, is presented. The data sample used corresponds to 139 fb1of proton-proton collisions at$$ \sqrt{s} $$s= 13 TeV collected during 2015–2018 with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting quark pairs (qq,bb,$$ t\overline{t} $$tt¯, andtb) or third-generation leptons (τνandττ) are included in this kind of combination for the first time. A simplified model predicting a spin-1 heavy vector-boson triplet is used. Cross-section limits are set at the 95% confidence level and are compared with predictions for the benchmark model. These limits are also expressed in terms of constraints on couplings of the heavy vector-boson triplet to quarks, leptons, and the Higgs boson. The complementarity of the various analyses increases the sensitivity to new physics, and the resulting constraints are stronger than those from any individual analysis considered. The data exclude a heavy vector-boson triplet with mass below 5.8 TeV in a weakly coupled scenario, below 4.4 TeV in a strongly coupled scenario, and up to 1.5 TeV in the case of production via vector-boson fusion.

     
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    Free, publicly-accessible full text available April 1, 2025
  5. Free, publicly-accessible full text available March 1, 2025
  6. A<sc>bstract</sc>

    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 fb1of proton-proton collisions collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Multiple signal regions are defined, targeting several SUSY simplified models yielding the desired final states. A single control region is used to constrain the normalisation of theWZ+ jets background. No significant excess of events over the Standard Model expectation is observed. The results are interpreted in the context of several supersymmetric models featuring R-parity conservation or R-parity violation, yielding exclusion limits surpassing those from previous searches. In models considering gluino (squark) pair production, gluino (squark) masses up to 2.2 (1.7) TeV are excluded at 95% confidence level.

     
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    Free, publicly-accessible full text available February 1, 2025
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  8. A<sc>bstract</sc>

    A search for new heavy scalars with flavour-violating decays in final states with multiple leptons andb-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 (ρtt,ρtc, andρtu). The targeted signals lead to final states with either a same-sign top-quark pair, three top-quarks, or four top-quarks. The search is based on a data sample of proton-proton collisions at$$ \sqrt{s} $$s= 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb1. Events are categorised depending on the multiplicity of light charged leptons (electrons or muons), total lepton charge, and a deep-neural-network output to enhance the purity of each of the signals. Masses of an additional scalar bosonmHbetween 200 − 630 GeV with couplingsρtt= 0.4,ρtc= 0.2, andρtu= 0.2 are excluded at 95% confidence level. Additional interpretations are provided in models ofR-parity violating supersymmetry, motivated by the recent flavour and (g −2)μanomalies.

     
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    Free, publicly-accessible full text available December 1, 2024