Browsing by Author "Hayrapetyan, A."

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    ArticlePublicationOpen Access
    Measurements of inclusive and differential cross sections for the Higgs boson production and decay to four-leptons in proton-proton collisions at √s=13 TeV
    (Springer, 2023-08-09) Hayrapetyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
    Measurements of the inclusive and differential fiducial cross sections for the Higgs boson production in the H -> ZZ -> 4 l ( l = e, mu) decay channel are presented. The results are obtained from the analysis of proton-proton collision data recorded by the CMS experiment at the CERN LHC at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 138 fb(-1). The measured inclusive fiducial cross section is 2.73 +/- 0.26 fb, in agreement with the standard model expectation of 2.86 +/- 0.1 fb. Differential cross sections are measured as a function of several kinematic observables sensitive to the Higgs boson production and decay to four leptons. A set of double-differential measurements is also performed, yielding a comprehensive characterization of the four leptons final state. Constraints on the Higgs boson trilinear coupling and on the bottom and charm quark coupling modifiers are derived from its transverse momentum distribution. All results are consistent with theoretical predictions from the standard model.
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    ArticlePublicationOpen Access
    Search for a high-mass dimuon resonance produced in association with b quark jets at √s=13 TeV
    (IEEE, 2023-10-06) Hayrapetyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
    A search for high-mass dimuon resonance production in association with one or more b quark jets is presented. The study uses proton-proton collision data collected with the CMS detector at the LHC corresponding to an integrated luminosity of 138 fb−1 at a center-of-mass energy of 13 TeV. Model-independent limits are derived on the number of signal events with exactly one or more than one b quark jet. Results are also interpreted in a lepton-flavor-universal model with Z′ boson couplings to a bb quark pair (gb), an sb quark pair (gbδbs), and any same-flavor charged lepton (gℓ) or neutrino pair (gν), with |gν| = |gℓ|. For a Z′ boson with a mass = 350 GeV (2 TeV) and |δbs| < 0.25, the majority of the parameter space with 0.0057 < |gℓ| < 0.35 (0.25 < |gℓ| < 0.43) and 0.0079 < |gb| < 0.46 (0.34 < |gb| < 0.57) is excluded at 95% confidence level. Finally, constraints are set on a Z′ model with parameters consistent with low-energy b → sℓℓ measurements. In this scenario, most of the allowed parameter space is excluded for a Z′ boson with 350 < < 500 GeV, while the constraints are less stringent for higher hypotheses. This is the first dedicated search at the LHC for a high-mass dimuon resonance produced in association with multiple b quark jets, and the constraints obtained on models with this signature are the most stringent to date.
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    ArticlePublicationOpen Access
    Search for new physics in multijet events with at least one photon and large missing transverse momentum in proton-proton collisions at 13 TeV
    (Springer, 2023-10-06) Hayrapetyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
    A search for new physics in final states consisting of at least one photon, multiple jets, and large missing transverse momentum is presented, using proton-proton collision events at a center-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 137 fb(-1), recorded by the CMS experiment at the CERN LHC from 2016 to 2018. The events are divided into mutually exclusive bins characterized by the missing transverse momentum, the number of jets, the number of b-tagged jets, and jets consistent with the presence of hadronically decaying W, Z, or Higgs bosons. The observed data are found to be consistent with the prediction from standard model processes. The results are interpreted in the context of simplified models of pair production of supersymmetric particles via strong and electroweak interactions. Depending on the details of the signal models, gluinos and squarks of masses up to 2.35 and 1.43 TeV, respectively, and electroweakinos of masses up to 1.23 TeV are excluded at 95% confidence level.
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    ArticlePublicationOpen Access
    Search for the lepton-flavor violating decay of the Higgs boson and additional Higgs bosons in the eμ final state in proton-proton collisions at √s = 13 TeV
    (American Physical Society, 2023-10-10) Hayrapetyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
    A search for the lepton-flavor violating decay of the Higgs boson and potential additional Higgs bosons with a mass in the range 110-160 GeV to an Formula Presented pair is presented. The search is performed with a proton-proton collision dataset at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of Formula Presented. No excess is observed for the Higgs boson. The observed (expected) upper limit on the Formula Presented branching fraction for it is determined to be Formula Presented at 95% confidence level, the most stringent limit set thus far from direct searches. The largest excess of events over the expected background in the full mass range of the search is observed at an Formula Presented invariant mass of approximately 146 GeV with a local (global) significance of 3.8 (2.8) standard deviations.