skip to main content


Search for: All records

Creators/Authors contains: "Ocalan, K."

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Free, publicly-accessible full text available October 1, 2025
  2. Abstract

    The operation and performance of the Compact Muon Solenoid (CMS) electromagnetic calorimeter (ECAL) are presented, based on data collected in pp collisions at √s=13 TeV at the CERN LHC, in the years from 2015 to 2018 (LHC Run 2), corresponding to an integrated luminosity of 151 fb-1. The CMS ECAL is a scintillating lead-tungstate crystal calorimeter, with a silicon strip preshower detector in the forward region that provides precise measurements of the energy and the time-of-arrival of electrons and photons. The successful operation of the ECAL is crucial for a broad range of physics goals, ranging from observing the Higgs boson and measuring its properties, to other standard model measurements and searches for new phenomena. Precise calibration, alignment, and monitoring of the ECAL response are important ingredients to achieve these goals. To face the challenges posed by the higher luminosity, which characterized the operation of the LHC in Run 2, the procedures established during the 2011–2012 run of the LHC have been revisited and new methods have been developed for the energy measurement and for the ECAL calibration. The energy resolution of the calorimeter, for electrons from Z boson decays reaching the ECAL without significant loss of energy by bremsstrahlung, was better than 1.8%, 3.0%, and 4.5% in the |η| intervals [0.0,0.8], [0.8,1.5], [1.5, 2.5], respectively. This resulting performance is similar to that achieved during Run 1 in 2011–2012, in spite of the more severe running conditions.

     
    more » « less
    Free, publicly-accessible full text available September 1, 2025
  3. A<sc>bstract</sc>

    Measurements of the charge-dependent two-particle angular correlation function in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of$$ \sqrt{s_{\textrm{NN}}} $$sNN= 8.16 TeV and lead-lead (PbPb) collisions at$$ \sqrt{s_{\textrm{NN}}} $$sNN= 5.02 TeV are reported. The pPb and PbPb data sets correspond to integrated luminosities of 186 nb1and 0.607 nb1, respectively, and were collected using the CMS detector at the CERN LHC. The charge-dependent correlations are characterized by balance functions of same- and opposite-sign particle pairs. The balance functions, which contain information about the creation time of charged particle pairs and the development of collectivity, are studied as functions of relative pseudorapidity (∆η) and relative azimuthal angle (∆ϕ), for various multiplicity and transverse momentum (pT) intervals. A multiplicity dependence of the balance function is observed in ∆ηand ∆ϕfor both systems. The width of the balance functions decreases towards high-multiplicity collisions in the momentum region<2 GeV, for pPb and PbPb results. Integrals of the balance functions are presented in both systems, and a mild dependence of the charge-balancing fractions on multiplicity is observed. No multiplicity dependence is observed at higher transverse momentum. The data are compared withhydjet,hijing, andamptgenerator predictions, none of which capture completely the multiplicity dependence seen in the data. The comparison of results with different center-of-mass energies suggests that the balance functions become narrower at higher energies, which is consistent with the idea of delayed hadronization and the effect of radial flow.

     
    more » « less
    Free, publicly-accessible full text available August 1, 2025
  4. The production ofϒ(2S)andϒ(3S)mesons in lead-lead (Pb-Pb) and proton-proton (pp) collisions is studied in their dimuon decay channel using the CMS detector at the LHC. Theϒ(3S)meson is observed for the first time in Pb-Pb collisions, with a significance above 5 standard deviations. The ratios of yields measured in Pb-Pb andppcollisions are reported for both theϒ(2S)andϒ(3S)mesons, as functions of transverse momentum and Pb-Pb collision centrality. These ratios, when appropriately scaled, are significantly less than unity, indicating a suppression ofϒyields in Pb-Pb collisions. This suppression increases from peripheral to central Pb-Pb collisions. Furthermore, the suppression is stronger forϒ(3S)mesons compared toϒ(2S)mesons, extending the pattern of sequential suppression of quarkonium states in nuclear collisions previously seen for theJ/ψ,ψ(2S),ϒ(1S), andϒ(2S)mesons.

    <supplementary-material><permissions><copyright-statement>© 2024 CERN, for the CMS 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 July 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/10537391-search-scalar-pseudoscalar-dilepton-resonance-produced-association-massive-vector-boson-top-quark-antiquark-pair-multilepton-events" itemprop="url"> <span class='span-link' itemprop="name">Search for a scalar or pseudoscalar dilepton resonance produced in association with a massive vector boson or top quark-antiquark pair in multilepton events at s=13  TeV</span> </a> </div> <div> <strong> <a class="misc external-link" href="https://doi.org/10.1103/PhysRevD.110.012013" target="_blank" title="Link to document DOI">https://doi.org/10.1103/PhysRevD.110.012013  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Tumasyan, A</span> <span class="sep">; </span><span class="author" itemprop="author">Adam, W</span> <span class="sep">; </span><span class="author" itemprop="author">Andrejkovic, J W</span> <span class="sep">; </span><span class="author" itemprop="author">Bergauer, T</span> <span class="sep">; </span><span class="author" itemprop="author">Chatterjee, S</span> <span class="sep">; </span><span class="author" itemprop="author">Damanakis, K</span> <span class="sep">; </span><span class="author" itemprop="author">Dragicevic, M</span> <span class="sep">; </span><span class="author" itemprop="author">Escalante_Del_Valle, A</span> <span class="sep">; </span><span class="author" itemprop="author">Hussain, P S</span> <span class="sep">; </span><span class="author" itemprop="author">Jeitler, M</span> <span class="sep">; </span><span class="author">et al</span></span> <span class="year">( <time itemprop="datePublished" datetime="2024-07-01">July 2024</time> , Physical Review D) </span> </div> <div style="cursor: pointer;-webkit-line-clamp: 5;" class="abstract" itemprop="description"> <p>A search for beyond the standard model spin-0 bosons,<math display='inline'><mi>ϕ</mi></math>, that decay into pairs of electrons, muons, or tau leptons is presented. The search targets the associated production of such bosons with a<math display='inline'><mi>W</mi></math>or<math display='inline'><mi>Z</mi></math>gauge boson, or a top quark-antiquark pair, and uses events with three or four charged leptons, including hadronically decaying tau leptons. The proton-proton collision data set used in the analysis was collected at the LHC from 2016 to 2018 at a center-of-mass energy of 13 TeV, and corresponds to an integrated luminosity of<math display='inline'><mn>138</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. The observations are consistent with the predictions from standard model processes. Upper limits are placed on the product of cross sections and branching fractions of such new particles over the mass range of 15 to 350 GeV with scalar, pseudoscalar, or Higgs-boson-like couplings, as well as on the product of coupling parameters and branching fractions. Several model-dependent exclusion limits are also presented. For a Higgs-boson-like<math display='inline'><mi>ϕ</mi></math>model, limits are set on the mixing angle of the Higgs boson with the<math display='inline'><mi>ϕ</mi></math>boson. For the associated production of a<math display='inline'><mi>ϕ</mi></math>boson with a top quark-antiquark pair, limits are set on the coupling to top quarks. Finally, limits are set for the first time on a fermiophilic dilaton-like model with scalar couplings and a fermiophilic axion-like model with pseudoscalar couplings.</p> <sec><title/><supplementary-material><permissions><copyright-statement>© 2024 CERN, for the CMS 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 July 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/10549903-search-high-mass-exclusive-diphoton-production-tagged-protons-proton-proton-collisions" itemprop="url"> <span class='span-link' itemprop="name">Search for high-mass exclusive diphoton production with tagged protons in proton-proton collisions at s=13  TeV</span> </a> </div> <div> <strong> <a class="misc external-link" href="https://doi.org/10.1103/PhysRevD.110.012010" target="_blank" title="Link to document DOI">https://doi.org/10.1103/PhysRevD.110.012010  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Tumasyan, A</span> <span class="sep">; </span><span class="author" itemprop="author">Adam, W</span> <span class="sep">; </span><span class="author" itemprop="author">Andrejkovic, J W</span> <span class="sep">; </span><span class="author" itemprop="author">Bergauer, T</span> <span class="sep">; </span><span class="author" itemprop="author">Chatterjee, S</span> <span class="sep">; </span><span class="author" itemprop="author">Damanakis, K</span> <span class="sep">; </span><span class="author" itemprop="author">Dragicevic, M</span> <span class="sep">; </span><span class="author" itemprop="author">Escalante_Del_Valle, A</span> <span class="sep">; </span><span class="author" itemprop="author">Hussain, P S</span> <span class="sep">; </span><span class="author" itemprop="author">Jeitler, M</span> <span class="sep">; </span><span class="author">et al</span></span> <span class="year">( <time itemprop="datePublished" datetime="2024-07-01">July 2024</time> , Physical Review D) </span> </div> <div style="cursor: pointer;-webkit-line-clamp: 5;" class="abstract" itemprop="description"> <p>A search is presented for high-mass exclusive diphoton production via photon-photon fusion in proton-proton collisions at<math display='inline'><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>in events where both protons survive the interaction. The analysis utilizes data corresponding to an integrated luminosity of<math display='inline'><mn>103</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>collected in 2016–2018 with the central CMS detector and the CMS and TOTEM precision proton spectrometer (PPS). Events that have two photons with high transverse momenta (<math display='inline'><mrow><msubsup><mrow><mi>p</mi></mrow><mrow><mi mathvariant='normal'>T</mi></mrow><mrow><mi>γ</mi></mrow></msubsup></mrow><mo>></mo><mn>100</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>), back-to-back in azimuth, and with a large diphoton invariant mass (<math display='inline'><msub><mi>m</mi><mrow><mi>γ</mi><mi>γ</mi></mrow></msub><mo>></mo><mn>350</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>) are selected. To remove the dominant inclusive diphoton backgrounds, the kinematic properties of the protons detected in PPS are required to match those of the central diphoton system. Only events having opposite-side forward protons detected with a fractional momentum loss between 0.035 and 0.15 (0.18) for the detectors on the negative (positive) side of CMS are considered. One exclusive diphoton candidate is observed for an expected background of 1.1 events. Limits at 95% confidence level are derived for the four-photon anomalous coupling parameters<math display='inline'><mrow><mo stretchy='false'>|</mo><msub><mi>ζ</mi><mn>1</mn></msub><mo stretchy='false'>|</mo></mrow><mo><</mo><mn>0.073</mn><mtext> </mtext><mtext> </mtext><msup><mi>TeV</mi><mrow><mo>−</mo><mn>4</mn></mrow></msup></math>and<math display='inline'><mrow><mo stretchy='false'>|</mo><msub><mi>ζ</mi><mn>2</mn></msub><mo stretchy='false'>|</mo></mrow><mo><</mo><mn>0.15</mn><mtext> </mtext><mtext> </mtext><msup><mi>TeV</mi><mrow><mo>−</mo><mn>4</mn></mrow></msup></math>, using an effective field theory. Additionally, upper limits are placed on the production of axionlike particles with coupling strength to photons<math display='inline'><msup><mi>f</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>that varies from<math display='inline'><mn>0.03</mn><mtext> </mtext><mtext> </mtext><msup><mi>TeV</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>to<math display='inline'><mn>1</mn><mtext> </mtext><mtext> </mtext><msup><mi>TeV</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>over the mass range from 500 to 2000 GeV.</p> <sec><title/><supplementary-material><permissions><copyright-statement>© 2024 CERN, for the CMS and TOTEMs 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 July 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/10549894-search-stealth-supersymmetry-final-states-two-photons-jets-low-missing-transverse-momentum-proton-proton-collisions" itemprop="url"> <span class='span-link' itemprop="name">Search for stealth supersymmetry in final states with two photons, jets, and low missing transverse momentum in proton-proton collisions at s=13  TeV</span> </a> </div> <div> <strong> <a class="misc external-link" href="https://doi.org/10.1103/PhysRevD.109.112009" target="_blank" title="Link to document DOI">https://doi.org/10.1103/PhysRevD.109.112009  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Hayrapetyan, A</span> <span class="sep">; </span><span class="author" itemprop="author">Tumasyan, A</span> <span class="sep">; </span><span class="author" itemprop="author">Adam, W</span> <span class="sep">; </span><span class="author" itemprop="author">Andrejkovic, J W</span> <span class="sep">; </span><span class="author" itemprop="author">Bergauer, T</span> <span class="sep">; </span><span class="author" itemprop="author">Chatterjee, S</span> <span class="sep">; </span><span class="author" itemprop="author">Damanakis, K</span> <span class="sep">; </span><span class="author" itemprop="author">Dragicevic, M</span> <span class="sep">; </span><span class="author" itemprop="author">Del_Valle, A Escalante</span> <span class="sep">; </span><span class="author" itemprop="author">Hussain, P 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>The results of a search for stealth supersymmetry in final states with two photons and jets, targeting a phase space region with low missing transverse momentum (<math display='inline'><mrow><msubsup><mrow><mi>p</mi></mrow><mrow><mi mathvariant='normal'>T</mi></mrow><mrow><mi>miss</mi></mrow></msubsup></mrow></math>), are reported. The study is based on a sample of proton-proton collisions at<math display='inline'><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mrow><mi>TeV</mi></mrow></mrow></math>collected by the CMS experiment, corresponding to an integrated luminosity of<math display='inline'><mn>138</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. As LHC results continue to constrain the parameter space of the minimal supersymmetric standard model, the low<math display='inline'><mrow><msubsup><mrow><mi>p</mi></mrow><mrow><mi mathvariant='normal'>T</mi></mrow><mrow><mi>miss</mi></mrow></msubsup></mrow></math>regime is increasingly valuable to explore. To estimate the backgrounds due to standard model processes in such events, we apply corrections derived from simulation to an estimate based on a control selection in data. The results are interpreted in the context of simplified stealth supersymmetry models with gluino and squark pair production. The observed data are consistent with the standard model predictions, and gluino (squark) masses of up to 2150 (1850) GeV are excluded at the 95% confidence level.</p> <sec><title/><supplementary-material><permissions><copyright-statement>© 2024 CERN, for the CMS 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/10549901-search-central-exclusive-production-top-quark-pairs-proton-proton-collisions-sqrt-tev-tagged-protons" itemprop="url"> <span class='span-link' itemprop="name">Search for central exclusive production of top quark pairs in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV with tagged protons</span> </a> </div> <div> <strong> <a class="misc external-link" href="https://doi.org/10.1007/JHEP06(2024)187" target="_blank" title="Link to document DOI">https://doi.org/10.1007/JHEP06(2024)187  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Tumasyan, A</span> <span class="sep">; </span><span class="author" itemprop="author">Adam, W</span> <span class="sep">; </span><span class="author" itemprop="author">Andrejkovic, J W</span> <span class="sep">; </span><span class="author" itemprop="author">Bergauer, T</span> <span class="sep">; </span><span class="author" itemprop="author">Chatterjee, S</span> <span class="sep">; </span><span class="author" itemprop="author">Damanakis, K</span> <span class="sep">; </span><span class="author" itemprop="author">Dragicevic, M</span> <span class="sep">; </span><span class="author" itemprop="author">Escalante_Del_Valle, A</span> <span class="sep">; </span><span class="author" itemprop="author">Hussain, P S</span> <span class="sep">; </span><span class="author" itemprop="author">Jeitler, M</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> , 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 search for the central exclusive production of top quark-antiquark pairs ($$ \textrm{t}\overline{\textrm{t}} $$tt¯) is performed for the first time using proton-tagged events in proton-proton collisions at the LHC at a centre-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 29.4 fb1. The$$ \textrm{t}\overline{\textrm{t}} $$tt¯decay products are reconstructed using the central CMS detector, while forward protons are measured in the CMS-TOTEM precision proton spectrometer. An observed (expected) upper bound on the production cross section of 0.59 (1.14) pb is set at 95% confidence level, for collisions of protons with fractional momentum losses between 2 and 20%.

     
    more » « less
    Free, publicly-accessible full text available June 1, 2025
  5. Differential cross sections are measured for the standard model Higgs boson produced in association with vector bosons (W,Z) and decaying to a pair ofbquarks. Measurements are performed within the framework of the simplified template cross sections. The analysis relies on the leptonic decays of theWandZbosons, resulting in final states with 0, 1, or 2 electrons or muons. The Higgs boson candidates are either reconstructed from pairs of resolvedb-tagged jets, or from single large-radius jets containing the particles arising from twobquarks. Proton-proton collision data ats=13TeV, collected by the CMS experiment in 2016–2018 and corresponding to a total integrated luminosity of138fb1, are analyzed. The inclusive signal strength, defined as the product of the observed production cross section and branching fraction relative to the standard model expectation, combining all analysis categories, is found to beμ=1.150.20+0.22. This corresponds to an observed (expected) significance of 6.3 (5.6) standard deviations.

    <supplementary-material><permissions><copyright-statement>© 2024 CERN, for the CMS 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 May 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/10549597-inclusive-differential-cross-section-measurements-textrm-overline-textrm-textrm-overline-textrm-production-lepton+jets-channel-sqrt-tev" itemprop="url"> <span class='span-link' itemprop="name">Inclusive and differential cross section measurements of $$ \textrm{t}\overline{\textrm{t}}\textrm{b}\overline{\textrm{b}} $$ production in the lepton+jets channel at $$ \sqrt{s} $$ = 13 TeV</span> </a> </div> <div> <strong> <a class="misc external-link" href="https://doi.org/10.1007/JHEP05(2024)042" target="_blank" title="Link to document DOI">https://doi.org/10.1007/JHEP05(2024)042  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Hayrapetyan, A</span> <span class="sep">; </span><span class="author" itemprop="author">Tumasyan, A</span> <span class="sep">; </span><span class="author" itemprop="author">Adam, W</span> <span class="sep">; </span><span class="author" itemprop="author">Andrejkovic, J W</span> <span class="sep">; </span><span class="author" itemprop="author">Bergauer, T</span> <span class="sep">; </span><span class="author" itemprop="author">Chatterjee, S</span> <span class="sep">; </span><span class="author" itemprop="author">Damanakis, K</span> <span class="sep">; </span><span class="author" itemprop="author">Dragicevic, M</span> <span class="sep">; </span><span class="author" itemprop="author">Escalante_Del_Valle, A</span> <span class="sep">; </span><span class="author" itemprop="author">Hussain, P 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>

    Measurements of inclusive and normalized differential cross sections of the associated production of top quark-antiquark and bottom quark-antiquark pairs,$$ \textrm{t}\overline{\textrm{t}}\textrm{b}\overline{\textrm{b}} $$tt¯bb¯, are presented. The results are based on data from proton-proton collisions collected by the CMS detector at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb1. The cross sections are measured in the lepton+jets decay channel of the top quark pair, using events containing exactly one isolated electron or muon and at least five jets. Measurements are made in four fiducial phase space regions, targeting different aspects of the$$ \textrm{t}\overline{\textrm{t}}\textrm{b}\overline{\textrm{b}} $$tt¯bb¯process. Distributions are unfolded to the particle level through maximum likelihood fits, and compared with predictions from several event generators. The inclusive cross section measurements of this process in the fiducial phase space regions are the most precise to date. In most cases, the measured inclusive cross sections exceed the predictions with the chosen generator settings. The only exception is when using a particular choice of dynamic renormalization scale,$$ {\mu}_{\textrm{R}}=\frac{1}{2}{\prod}_{i=\textrm{t},\overline{\textrm{t}},\textrm{b},\overline{\textrm{b}}}{m}_{\textrm{T},i}^{1/4} $$μR=12i=t,t¯,b,b¯mT,i1/4, where$$ {m}_{\textrm{T},i}^2={m}_i^2+{p}_{\textrm{T},i}^2 $$mT,i2=mi2+pT,i2are the transverse masses of top and bottom quarks. The differential cross sections show varying degrees of compatibility with the theoretical predictions, and none of the tested generators with the chosen settings simultaneously describe all the measured distributions.

     
    more » « less
    Free, publicly-accessible full text available May 1, 2025