Browsing by Author "Hussain, P. S."

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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: 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: 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: 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.