Showing papers by "Armen Tumasyan published in 2023"
4 citations
TL;DR: In this paper , the authors presented a search for direct production of charginos and neutralinos via electroweak interactions, based on data from proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb−1.
1 citations
TL;DR: In this paper , the Bs0→μ+μ− branching fraction and effective lifetime of the Bn0 meson were measured at the LHC with an integrated luminosity of 140fb−1.
1 citations
TL;DR: In this paper , a search for pairs of light Higgs bosons produced in supersymmetric cascade decays in final states with small missing transverse momentum is reported, and results from the search are interpreted in the next-to-minimal superymmetric extension of the SM, where a “singlino” of small mass leads to squark and gluino cascades that can predominantly end in a highly Lorentz-boosted singlet-like boson.
Abstract: Abstract A search is reported for pairs of light Higgs bosons ( $${\textrm{H}} _1$$ H 1 ) produced in supersymmetric cascade decays in final states with small missing transverse momentum. A data set of LHC $$\hbox {pp}$$ pp collisions collected with the CMS detector at $$\sqrt{s}=13\,\text {TeV} $$ s = 13 TeV and corresponding to an integrated luminosity of 138 $$\,\text {fb}^{-1}$$ fb - 1 is used. The search targets events where both $${\textrm{H}} _1$$ H 1 bosons decay into "Equation missing" pairs that are reconstructed as large-radius jets using substructure techniques. No evidence is found for an excess of events beyond the background expectations of the standard model (SM). Results from the search are interpreted in the next-to-minimal supersymmetric extension of the SM, where a “singlino” of small mass leads to squark and gluino cascade decays that can predominantly end in a highly Lorentz-boosted singlet-like $${\textrm{H}} _1$$ H 1 and a singlino-like neutralino of small transverse momentum. Upper limits are set on the product of the squark or gluino pair production cross section and the square of the "Equation missing" branching fraction of the $${\textrm{H}} _1$$ H 1 in a benchmark model containing almost mass-degenerate gluinos and light-flavour squarks. Under the assumption of an SM-like "Equation missing" branching fraction, $${\textrm{H}} _1$$ H 1 bosons with masses in the range 40–120 $$\,\text {GeV}$$ GeV arising from the decays of squarks or gluinos with a mass of 1200–2500 $$\,\text {GeV}$$ GeV are excluded at 95% confidence level.
TL;DR: In this article , a search for heavy resonances and quantum black holes decaying into eμ, eτ, and μτ final states in proton-proton collision data recorded by the CERN LHC during 2016-2018 at = 13 TeV, corresponding to an integrated luminosity of 138 fb − 1 .
Abstract: A bstract A search is reported for heavy resonances and quantum black holes decaying into eμ, eτ, and μτ final states in proton-proton collision data recorded by the CMS experiment at the CERN LHC during 2016–2018 at $$ \sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 138 fb − 1 . The eμ, eτ, and μτ invariant mass spectra are reconstructed, and no evidence is found for physics beyond the standard model. Upper limits are set at 95% confidence level on the product of the cross section and branching fraction for lepton flavor violating signals. Three benchmark signals are studied: resonant τ sneutrino production in R parity violating supersymmetric models, heavy Z′ gauge bosons with lepton flavor violating decays, and nonresonant quantum black hole production in models with extra spatial dimensions. Resonant τ sneutrinos are excluded for masses up to 4.2TeV in the eμ channel, 3.7TeV in the eτ channel, and 3.6TeV in the μτ channel. A Z′ boson with lepton flavor violating couplings is excluded up to a mass of 5.0TeV in the eμ channel, up to 4.3Te V in the eτ channel, and up to 4.1TeV in the μτ channel. Quantum black holes in the benchmark model are excluded up to the threshold mass of 5.6TeV in the eμ channel, 5.2TeV in the eτ channel, and 5.0TeV in the μτ channel. In addition, model-independent limits are extracted to allow comparisons with other models for the same final states and similar event selection requirements. The results of these searches provide the most stringent limits available from collider experiments for heavy particles that undergo lepton flavor violating decays.
TL;DR: The first search exploiting the vector boson fusion process to probe heavy Majorana neutrinos and the Weinberg operator at the LHC is presented in this article , where the search is performed in the same-sign dimuon final state using a proton-proton collision dataset recorded with the CMS detector and corresponding to a total integrated luminosity of 138.
Abstract: The first search exploiting the vector boson fusion process to probe heavy Majorana neutrinos and the Weinberg operator at the LHC is presented. The search is performed in the same-sign dimuon final state using a proton-proton collision dataset recorded at sqrt[s]=13 TeV, collected with the CMS detector and corresponding to a total integrated luminosity of 138 fb^{-1}. The results are found to agree with the predictions of the standard model. For heavy Majorana neutrinos, constraints on the squared mixing element between the muon and the heavy neutrino are derived in the heavy neutrino mass range 50 GeV-25 TeV; for masses above 650 GeV these are the most stringent constraints from searches at the LHC to date. A first test of the Weinberg operator at colliders provides an observed upper limit at 95% confidence level on the effective μμ Majorana neutrino mass of 10.8 GeV.
13 Jul 2023
17 Jul 2023
TL;DR: In this article , a search for nonresonant production of Higgs boson pairs via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two tau leptons is presented.
TL;DR: In this article , a measurement of the jet mass distribution in hadronic decays of Lorentz-boosted top quarks is presented, where the lepton is an electron or muon.
Abstract: Abstract A measurement of the jet mass distribution in hadronic decays of Lorentz-boosted top quarks is presented. The measurement is performed in the lepton + jets channel of top quark pair production ( $$\hbox {t}\overline{\hbox {t}}$$ t t ¯ ) events, where the lepton is an electron or muon. The products of the hadronic top quark decay are reconstructed using a single large-radius jet with transverse momentum greater than 400 $$\,\text {Ge}\hspace{-.08em}\text {V}$$ Ge V . The data were collected with the CMS detector at the LHC in proton-proton collisions and correspond to an integrated luminosity of 138 $$\,\text {fb}^{-1}$$ fb - 1 . The differential $$\hbox {t}\overline{\hbox {t}}$$ t t ¯ production cross section as a function of the jet mass is unfolded to the particle level and is used to extract the top quark mass. The jet mass scale is calibrated using the hadronic W boson decay within the large-radius jet. The uncertainties in the modelling of the final state radiation are reduced by studying angular correlations in the jet substructure. These developments lead to a significant increase in precision, and a top quark mass of $$173.06 \pm 0.84\,\text {Ge}\hspace{-.08em}\text {V} $$ 173.06 ± 0.84 Ge V .
TL;DR: In this paper , a search for pairs of light Higgs bosons produced in supersymmetric cascade decays in final states with small missing transverse momentum is reported, and results from the search are interpreted in the next-to-minimal superymmetric extension of the SM, where a “singlino” of small mass leads to squark and gluino cascades that can predominantly end in a highly Lorentz-boosted singlet-like boson.
Abstract: Abstract A search is reported for pairs of light Higgs bosons ( $${\textrm{H}} _1$$ H 1 ) produced in supersymmetric cascade decays in final states with small missing transverse momentum. A data set of LHC $$\hbox {pp}$$ pp collisions collected with the CMS detector at $$\sqrt{s}=13\,\text {TeV} $$ s = 13 TeV and corresponding to an integrated luminosity of 138 $$\,\text {fb}^{-1}$$ fb - 1 is used. The search targets events where both $${\textrm{H}} _1$$ H 1 bosons decay into "Equation missing" pairs that are reconstructed as large-radius jets using substructure techniques. No evidence is found for an excess of events beyond the background expectations of the standard model (SM). Results from the search are interpreted in the next-to-minimal supersymmetric extension of the SM, where a “singlino” of small mass leads to squark and gluino cascade decays that can predominantly end in a highly Lorentz-boosted singlet-like $${\textrm{H}} _1$$ H 1 and a singlino-like neutralino of small transverse momentum. Upper limits are set on the product of the squark or gluino pair production cross section and the square of the "Equation missing" branching fraction of the $${\textrm{H}} _1$$ H 1 in a benchmark model containing almost mass-degenerate gluinos and light-flavour squarks. Under the assumption of an SM-like "Equation missing" branching fraction, $${\textrm{H}} _1$$ H 1 bosons with masses in the range 40–120 $$\,\text {GeV}$$ GeV arising from the decays of squarks or gluinos with a mass of 1200–2500 $$\,\text {GeV}$$ GeV are excluded at 95% confidence level.
TL;DR: In this article , a search for the pair production of the lightest supersymmetric partner of the top quark, the top squark ($\tilde{\mathrm{t}}_1$), is presented.
Abstract: A search for the pair production of the lightest supersymmetric partner of the top quark, the top squark ($\tilde{\mathrm{t}}_1$), is presented. The search targets the four-body decay of the $\tilde{\mathrm{t}}_1$, which is preferred when the mass difference between the top squark and the lightest supersymmetric particle is smaller than the mass of the W boson. This decay mode consists of a bottom quark, two other fermions, and the lightest neutralino ($\tilde{\chi}^0_1$), which is assumed to be the lightest supersymmetric particle. The data correspond to an integrated luminosity of 138 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC. Events are selected using the presence of a high-momentum jet, an electron or muon with low transverse momentum, and a significant missing transverse momentum. The signal is selected based on a multivariate approach that is optimized for the difference between $m(\tilde{\mathrm{t}}_1)$ and $m(\tilde{\chi}^0_1)$. The contribution from leading background processes is estimated from data. No significant excess is observed above the expectation from standard model processes. The results of this search exclude top squarks at 95% confidence level for masses up to 480 and 700 GeV for $m(\tilde{\mathrm{t}}_1) - m(\tilde{\chi}^0_1$) = 10 and 80 GeV, respectively.
TL;DR: In this paper , the authors search for decays of the Higgs boson into a Z boson and a J/$\psi$ or π$(2S) meson in four-lepton final states with the LHC.
01 Feb 2023
01 Jul 2023
TL;DR: In this paper , a search for CP violation in the production and decay of top quark-antiquark pairs in the lepton+jets channel was conducted based on data from proton-proton collisions at 13 TeV.
Abstract: Results are presented on a search for CP violation in the production and decay of top quark-antiquark pairs in the lepton+jets channel. The search is based on data from proton-proton collisions at 13 TeV, collected with the CMS detector, corresponding to an integrated luminosity of 138 fb$^{-1}$. Possible CP violation effects are evaluated by measuring uncorrected asymmetries in observables constructed from linearly independent four-momentum vectors of the final-state particles. The dimensionless chromoelectric dipole moment of the top quark obtained from the observed asymmetries is measured to be 0.04 $\pm$ 0.10 (stat) $\pm$ 0.07 (syst), and the asymmetries exhibit no evidence for CP-violating effects, consistent with expectations from the standard model.
TL;DR: The first search exploiting the vector boson fusion process to probe heavy Majorana neutrinos and the Weinberg operator at the LHC is presented in this paper , which is performed in the same-sign dimuon final state using a proton-proton collision dataset recorded at s=13 TeV, collected with the CMS detector and corresponding to a total integrated luminosity of 138 fb−1.
Abstract: The first search exploiting the vector boson fusion process to probe heavy Majorana neutrinos and the Weinberg operator at the LHC is presented. The search is performed in the same-sign dimuon final state using a proton-proton collision dataset recorded at s=13 TeV, collected with the CMS detector and corresponding to a total integrated luminosity of 138 fb−1. The results are found to agree with the predictions of the standard model. For heavy Majorana neutrinos, constraints on the squared mixing element between the muon and the heavy neutrino are derived in the heavy neutrino mass range 50 GeV–25 TeV; for masses above 650 GeV these are the most stringent constraints from searches at the LHC to date. A first test of the Weinberg operator at colliders provides an observed upper limit at 95% confidence level on the effective μμ Majorana neutrino mass of 10.8 GeV.Received 17 June 2022Accepted 31 August 2022DOI:https://doi.org/10.1103/PhysRevLett.131.011803Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2023 CERN, for the CMS CollaborationPhysics Subject Headings (PhySH)Research AreasW & Z bosonsPhysical SystemsMajorana neutrinosTechniquesHadron collidersParticles & Fields
TL;DR: In this article , a neural network based analysis and an analysis based on an event categorization optimized on the ratio of signal over background events are presented, complemented by an analysis targeting vector boson associated Higgs boson production.
Abstract: Measurements of Higgs boson production, where the Higgs boson decays into a pair of $\tau$ leptons, are presented, using a sample of proton-proton collisions collected with the CMS experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. Three analyses are presented. Two are targeting Higgs boson production via gluon fusion and vector boson fusion: a neural network based analysis and an analysis based on an event categorization optimized on the ratio of signal over background events. These are complemented by an analysis targeting vector boson associated Higgs boson production. Results are presented in the form of signal strengths relative to the standard model predictions and products of cross sections and branching fraction to $\tau$ leptons, in up to 16 different kinematic regions. For the simultaneous measurements of the neural network based analysis and the analysis targeting vector boson associated Higgs boson production signal strengths are found to be 0.82 $\pm$ 0.11 for inclusive Higgs boson production, 0.67 $\pm$ 0.19 (0.81 $\pm$ 0.17) for the production mainly via gluon fusion (vector boson fusion), and 1.79 $\pm$ 0.45 for vector boson associated Higgs boson production.