Browsing by Author "Tumasyan, A. R."

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Citation - WoS: 1
Citation - Scopus: 4
Evidence for tWZ Production in Proton-Proton Collisions at S=13 TeV in Multilepton Final States
(Elsevier B.V., 2024) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Hussain, P. S.
The first evidence for the standard model production of a top quark in association with a W boson and a Z boson is reported. The measurement is performed in multilepton final states, where the Z boson is reconstructed via its decays to electron or muon pairs. At least one W boson, associated or from top quark decay, decays leptonically, too. The analysed data were recorded by the CMS experiment at the CERN LHC in 2016–2018 in proton-proton collisions at s=13 TeV, and correspond to an integrated luminosity of 138 fb−1. The measured cross section is 354±54(stat)±95(syst) fb, and corresponds to a statistical significance of 3.4 standard deviations. © 2025 Elsevier B.V., All rights reserved.
Citation - Scopus: 1
Measurement of Inclusive and Differential Cross Sections of Single Top Quark Production in Association with a W Boson in Proton-Proton Collisions at s = 13.6 TeV
(Springer Science and Business Media Deutschland GmbH, 2025) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Jeitler, Manfred A.
The first measurement of the inclusive and normalised differential cross sections of single top quark production in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13.6 TeV is presented. The data were recorded with the CMS detector at the LHC in 2022, and correspond to an integrated luminosity of 34.7 fb−1. The analysed events contain one muon and one electron in the final state. For the inclusive measurement, multivariate discriminants exploiting the kinematic properties of the events are used to separate the signal from the dominant top quark-antiquark production background. A cross section of 82.3±2.1stat−9.7+9.9syst±3.3lumi pb is obtained, consistent with the predictions of the standard model. A fiducial region is defined according to the detector acceptance to perform the differential measurements. The resulting differential distributions are unfolded to particle level and show good agreement with the predictions at next-to-leading order in perturbative quantum chromodynamics. © 2025 Elsevier B.V., All rights reserved.
Measurement of the Inclusive Tt¯ Cross Section in Final States with at least One Lepton and Additional Jets with 302 Pb−1 of Pp Collisions at S = 5.02 TeV
(Springer Science and Business Media Deutschland GmbH, 2025) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Jeitler, Manfred A.
A measurement of the top quark pair (tt¯) production cross section in proton-proton collisions at a centre-of-mass energy of 5.02 TeV is presented. The data were collected at the LHC in autumn 2017, in dedicated runs with low-energy and low-intensity conditions with respect to the default configuration, and correspond to an integrated luminosity of 302 pb−1. The measurement is performed using events with one electron or muon, and multiple jets, at least one of them being identified as originating from a b quark (b tagged). Events are classified based on the number of all reconstructed jets and of b-tagged jets. Multivariate analysis techniques are used to enhance the separation between the signal and backgrounds. The measured cross section is 62.5±1.6stat−2.5+2.6syst±1.2lumi pb. A combination with the result in the dilepton channel based on the same data set yields a value of 62.3 ± 1.5 (stat) ± 2.4 (syst) ± 1.2 (lumi) pb, to be compared with the standard model prediction of 69.5−3.7+3.5 pb at next-to-next-to-leading order in perturbative quantum chromodynamics. © 2025 Elsevier B.V., All rights reserved.
Citation - Scopus: 2
Measurement of the Inclusive WZ Production Cross Section in Pp Collisions at S = 13.6 TeV
(Springer Science and Business Media Deutschland GmbH, 2025) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Benato, Lisa; Bergauer, Thomas; Hussain, P. S.
The inclusive WZ production cross section is measured in proton-proton collisions at a centre-of-mass energy of 13.6 TeV, using data collected during 2022 with the CMS detector, corresponding to an integrated luminosity of 34.7 fb−1. The measurement uses multileptonic final states and a simultaneous likelihood fit to the number of events in four different lepton flavour categories: eee, eeμ, μμe, and μμμ. The selection is optimized to minimize the number of background events, and relies on an efficient prompt lepton discrimination strategy. The WZ production cross section is measured in a phase space defined within a 30 GeV window around the Z boson mass, as σtotal (pp → WZ) = 55.2 ± 1.2 (stat) ± 1.2 (syst) ± 0.8 (lumi) ± 0.3 (theo) pb. In addition, the cross section is measured in a fiducial phase space closer to the detector-level requirements. All the measurements presented in this paper are in agreement with standard model predictions. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 4
Citation - Scopus: 6
Measurement of the Polarizations of Prompt and Non-Prompt J/Ψ and Ψ(2s) Mesons Produced in pp Collisions at √s = 13 TeV
(Elsevier B.V., 2024) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Jeitler, Manfred A.
The polarizations of prompt and non-prompt [Formula presented] and ψ(2S) mesons are measured in proton-proton collisions at s=13 TeV, using data samples collected by the CMS experiment in 2017 and 2018, corresponding to a total integrated luminosity of 103.3fb−1. Based on the analysis of the dimuon decay angular distributions in the helicity frame, the polar anisotropy, λϑ, is measured as a function of the transverse momentum, pT, of the charmonium states, in the 25–120 and 20–100 GeV ranges for the [Formula presented] and ψ(2S), respectively. The non-prompt polarizations agree with predictions based on the hypothesis that, for pT≳25GeV, the non-prompt [Formula presented] and ψ(2S) are predominantly produced in two-body B meson decays. The prompt results clearly exclude strong transverse polarizations, even for pT exceeding 30 times the [Formula presented] mass, where λϑ tends to an asymptotic value around 0.3. Taken together with previous measurements, by CMS and LHCb at s=7 TeV, the prompt polarizations show a significant variation with pT, at low pT. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 1
Citation - Scopus: 4
Model-Independent Search for Pair Production of New Bosons Decaying into Muons in Proton-Proton Collisions at √s = 13 TeV
(Springer Science and Business Media Deutschland GmbH, 2024) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Jeitler, Manfred A.
The results of a model-independent search for the pair production of new bosons within a mass range of 0.21 < m < 60 GeV, are presented. This study utilizes events with a four-muon final state. We use two data sets, comprising 41.5 fb−1 and 59.7 fb−1 of proton-proton collisions at s = 13 TeV, recorded in 2017 and 2018 by the CMS experiment at the CERN LHC. The study of the 2018 data set includes a search for displaced signatures of a new boson within the proper decay length range of 0 < cτ < 100 mm. Our results are combined with a previous CMS result, based on 35.9 fb−1 of proton-proton collisions at s = 13 TeV collected in 2016. No significant deviation from the expected background is observed. Results are presented in terms of a model-independent upper limit on the product of cross section, branching fraction, and acceptance. The findings are interpreted across various benchmark models, such as an axion-like particle model, a vector portal model, the next-to-minimal supersymmetric standard model, and a dark supersymmetric scenario, including those predicting a non-negligible proper decay length of the new boson. In all considered scenarios, substantial portions of the parameter space are excluded, expanding upon prior results. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 1
Citation - Scopus: 2
Search for a Heavy Resonance Decaying into a Z and a Higgs Boson in Events with an Energetic Jet and Two Electrons, Two Muons, or Missing Transverse Momentum in Proton-Proton Collisions at S = 13 TeV
(Springer Science and Business Media Deutschland GmbH, 2025) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Jeitler, Manfred A.
A search is presented for a heavy resonance decaying into a Z boson and a Higgs (H) boson. The analysis is based on data from proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb−1, recorded with the CMS experiment in the years 2016–2018. Resonance masses between 1.4 and 5 TeV are considered, resulting in large transverse momenta of the Z and H bosons. Final states that result from Z boson decays to pairs of electrons, muons, or neutrinos are considered. The H boson is reconstructed as a single large-radius jet, recoiling against the Z boson. Machine-learning flavour-tagging techniques are employed to identify decays of a Lorentz-boosted H boson into pairs of charm or bottom quarks, or into four quarks via the intermediate H → WW* and ZZ* decays. The analysis targets H boson decays that were not generally included in previous searches using the H → bb¯ channel. Compared with previous analyses, the sensitivity for high resonance masses is improved significantly in the channel where at most one b quark is tagged. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 5
Citation - Scopus: 6
Search for an Exotic Decay of the Higgs Boson into a Z Boson and a Pseudoscalar Particle in Proton-Proton Collisions at S=13 TeV
(Elsevier B.V., 2024) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Hussain, P. S.
A search for an exotic decay of the Higgs boson to a Z boson and a light pseudoscalar particle (a), decaying to a pair of leptons and a pair of photons, respectively, is presented. The search is based on proton-proton collision data at a center-of-mass energy of s=13TeV, collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 138fb−1. The analysis probes pseudoscalar masses ma between 1 and 30 GeV, leading to two pairs of well-isolated leptons and photons. Upper limits at 95% confidence level are set on the Higgs boson production cross section times its branching fraction to two leptons and two photons. The observed (expected) limits are in the range of 1.1–17.8 (1.7–17.9) fb within the probed ma interval. An excess of data above the expected standard model background with a local (global) significance of 2.6 (1.3) standard deviations is observed for a mass hypothesis of ma=3GeV. Limits on models involving axion-like particles, formulated as an effective field theory, are also reported. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 1
Citation - Scopus: 3
Search for Central Exclusive Production of Top Quark Pairs in Proton-Proton Collisions at √s = 13 TeV with Tagged Protons
(Springer Science and Business Media Deutschland GmbH, 2024) Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Damanakis, Konstantinos; Jeitler, Manfred A.
A search for the central exclusive production of top quark-antiquark pairs (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 fb−1. The 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%. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 1
Citation - Scopus: 2
Search for Heavy Long-Lived Charged Particles with Large Ionization Energy Loss in Proton-Proton Collisions at S = 13 TeV
(Springer Science and Business Media Deutschland GmbH, 2025) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Benato, Lisa; Bergauer, Thomas; Hussain, P. S.
A search for heavy, long-lived, charged particles with large ionization energy loss within the silicon tracker of the CMS experiment is presented. A data set of proton-proton collisions at a center of mass energy at s = 13 TeV, collected in 2017 and 2018 at the CERN LHC, corresponding to an integrated luminosity of 101 fb−1, is used in this analysis. Two different approaches for the search are taken. A new method exploits the independence of the silicon pixel and strips measurements, while the second method improves on previous techniques using ionization to determine a mass selection. No significant excess of events above the background expectation is observed. The results are interpreted in the context of the pair production of supersymmetric particles, namely gluinos, top squarks, and tau sleptons, and of the Drell-Yan pair production of fourth generation (τ′) leptons with an electric charge equal to or twice the absolute value of the electron charge (e). An interpretation of a Z’ boson decaying to two τ′ leptons with an electric charge equal to 2e is presented for the first time. The 95% confidence upper limits on the production cross section are extracted for each of these hypothetical particles. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 20
Citation - Scopus: 21
Search for Heavy Neutral Leptons in Final States with Electrons, Muons, and Hadronically Decaying Tau Leptons in Proton-Proton Collisions at √s = 13 TeV
(Springer Science and Business Media Deutschland GmbH, 2024) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Jeitler, Manfred A.
A search for heavy neutral leptons (HNLs) of Majorana or Dirac type using proton-proton collision data at s = 13 TeV is presented. The data were collected by the CMS experiment at the CERN LHC and correspond to an integrated luminosity of 138 fb−1. Events with three charged leptons (electrons, muons, and hadronically decaying tau leptons) are selected, corresponding to HNL production in association with a charged lepton and decay of the HNL to two charged leptons and a standard model (SM) neutrino. The search is performed for HNL masses between 10 GeV and 1.5 TeV. No evidence for an HNL signal is observed in data. Upper limits at 95% confidence level are found for the squared coupling strength of the HNL to SM neutrinos, considering exclusive coupling of the HNL to a single SM neutrino generation, for both Majorana and Dirac HNLs. The limits exceed previously achieved experimental constraints for a wide range of HNL masses, and the limits on tau neutrino coupling scenarios with HNL masses above the W boson mass are presented for the first time. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 9
Citation - Scopus: 13
Search for Long-Lived Heavy Neutrinos in the Decays of B Mesons Produced in Proton-Proton Collisions at S = 13 TeV
(Springer Science and Business Media Deutschland GmbH, 2024) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Jeitler, Manfred A.
A search for long-lived heavy neutrinos (N) in the decays of B mesons produced in proton-proton collisions at s = 13 TeV is presented. The data sample corresponds to an integrated luminosity of 41.6 fb−1 collected in 2018 by the CMS experiment at the CERN LHC, using a dedicated data stream that enhances the number of recorded events containing B mesons. The search probes heavy neutrinos with masses in the range 1 < mN < 3 GeV and decay lengths in the range 10−2 < cτN < 104 mm, where τN is the N proper mean lifetime. Signal events are defined by the signature B → ℓBNX; N → ℓ±π∓, where the leptons ℓB and ℓ can be either a muon or an electron, provided that at least one of them is a muon. The hadronic recoil system, X, is treated inclusively and is not reconstructed. No significant excess of events over the standard model background is observed in any of the ℓ±π∓ invariant mass distributions. Limits at 95% confidence level on the sum of the squares of the mixing amplitudes between heavy and light neutrinos, |VN|2, and on cτN are obtained in different mixing scenarios for both Majorana and Dirac-like N particles. The most stringent upper limit |VN|2 < 2.0 × 10−5 is obtained at mN = 1.95 GeV for the Majorana case where N mixes exclusively with muon neutrinos. The limits on |VN|2 for masses 1 < mN < 1.7 GeV are the most stringent from a collider experiment to date. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 8
Citation - Scopus: 5
Search for New Higgs Bosons via Same-Sign Top Quark Pair Production in Association with a Jet in Proton-Proton Collisions at S=13 TeV
(Elsevier B.V., 2024) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Jeitler, Manfred A.
A search is presented for new Higgs bosons in proton-proton (pp) collision events in which a same-sign top quark pair is produced in association with a jet, via the pp→tH/A→ttc‾ and pp→tH/A→ttu‾ processes. Here, H and A represent the extra scalar and pseudoscalar boson, respectively, of the second Higgs doublet in the generalized two-Higgs-doublet model (g2HDM). The search is based on pp collision data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb−1. Final states with a same-sign lepton pair in association with jets and missing transverse momentum are considered. New Higgs bosons in the 200–1000 GeV mass range and new Yukawa couplings between 0.1 and 1.0 are targeted in the search, for scenarios in which either H or A appear alone, or in which they coexist and interfere. No significant excess above the standard model prediction is observed. Exclusion limits are derived in the context of the g2HDM. © 2025 Elsevier B.V., All rights reserved.
Citation - Scopus: 2
Search for Resonant Pair Production of Higgs Bosons in the Bb¯Bb¯ Final State Using Large-Area Jets in Proton-Proton Collisions at S = 13 TeV
(Springer Science and Business Media Deutschland GmbH, 2025) Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Damanakis, Konstantinos; Jeitler, Manfred A.
A search is presented for the resonant production of a pair of standard model-like Higgs bosons using data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected by the CMS experiment at the CERN LHC in 2016–2018, corresponding to an integrated luminosity of 138 fb−1. The final state consists of two b quark-antiquark pairs. The search is conducted in the region of phase space where at least one of the pairs is highly Lorentz-boosted and is reconstructed as a single large-area jet. The other pair may be either similarly merged or resolved, the latter reconstructed using two b-tagged jets. The data are found to be consistent with standard model processes and are interpreted as 95% confidence level upper limits on the product of the cross sections and the branching fractions of the spin-0 radion and the spin-2 bulk graviton that arise in warped extradimensional models. The limits set are in the range 9.74–0.29 fb and 4.94–0.19 fb for a narrow radion and a graviton, respectively, with masses between 1 and 3 TeV. For a radion and for a bulk graviton with widths 10% of their masses, the limits are in the range 12.5–0.35 fb and 8.23–0.23 fb, respectively, for the same masses. These limits result in the exclusion of a narrow-width graviton with a mass below 1.2 TeV, and of narrow and 10%-width radions with masses below 2.6, and 2.9 TeV, respectively. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 3
Citation - Scopus: 6
Study of Azimuthal Anisotropy of ϒ(1s) Mesons in pPb Collisions at √snn = 8.16 TeV
(Elsevier B.V., 2024) Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Damanakis, Konstantinos; Jeitler, Manfred A.
The azimuthal anisotropy of [Formula presented] mesons in high-multiplicity proton-lead collisions is studied using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 8.16TeV. The [Formula presented] mesons are reconstructed using their dimuon decay channel. The anisotropy is characterized by the second Fourier harmonic coefficients, found using a two-particle correlation technique, in which the [Formula presented] mesons are correlated with charged hadrons. A large pseudorapidity gap is used to suppress short-range correlations. Nonflow contamination from the dijet background is removed using a low-multiplicity subtraction method, and the results are presented as a function of [Formula presented] transverse momentum. The azimuthal anisotropies are smaller than those found for charmonia in proton-lead collisions at the same collision energy, but are consistent with values found for [Formula presented] mesons in lead-lead interactions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. © 2025 Elsevier B.V., All rights reserved.
Citation - WoS: 17
Citation - Scopus: 23
Test of Lepton Flavor Universality in B ± → K ± Μ + Μ − and B ± → K ± E + E − Decays in Proton-Proton Collisions at S = 13 TeV
(Institute of Physics, 2024) Hayrapetyan, Aram A.; Tumasyan, A. R.; Adam, Wolfgang; Andrejkovic, J. W.; Bergauer, Thomas; Chatterjee, Suman; Jeitler, Manfred A.
A test of lepton flavor universality in B ± → K ± μ + μ − and B ± → K ± e + e − decays, as well as a measurement of differential and integrated branching fractions of a nonresonant B ± → K ± μ + μ − decay are presented. The analysis is made possible by a dedicated data set of proton-proton collisions at s = 13 TeV recorded in 2018, by the CMS experiment at the LHC, using a special high-rate data stream designed for collecting about 10 billion unbiased b hadron decays. The ratio of the branching fractions B ( B ± → K ± μ + μ − ) to B ( B ± → K ± e + e − ) is determined from the measured double ratio R ( K ) of these decays to the respective branching fractions of the B ± → J / ψ K ± with J / ψ → μ + μ − and e + e − decays, which allow for significant cancellation of systematic uncertainties. The ratio R ( K ) is measured in the range 1.1 < q 2 < 6.0 GeV 2 , where q is the invariant mass of the lepton pair, and is found to be R ( K ) = 0.78 − 0.23 + 0.47 , in agreement with the standard model expectation R ( K ) ≈ 1 . This measurement is limited by the statistical precision of the electron channel. The integrated branching fraction in the same q 2 range, B ( B ± → K ± μ + μ − ) = ( 12.42 ± 0.68 ) × 10 − 8 , is consistent with the present world-average value and has a comparable precision. © 2025 Elsevier B.V., All rights reserved.