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Öğe Higher-order moments of the elliptic flow distribution in PbPb collisions at sNN = 5.02 TeV(Springer Science and Business Media Deutschland GmbH, 2024) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.The hydrodynamic flow-like behavior of charged hadrons in high-energy lead-lead collisions is studied through multiparticle correlations. The elliptic anisotropy values based on different orders of multiparticle cumulants, v2{2k}, are measured up to the tenth order (k = 5) as functions of the collision centrality at a nucleon-nucleon center-of-mass energy of sNN = 5.02 TeV. The data were recorded by the CMS experiment at the LHC and correspond to an integrated luminosity of 0.607 nb?1. A hierarchy is observed between the coefficients, with v2{2} > v2{4} ? v2{6} ? v2{8} ? v2{10}. Based on these results, centrality-dependent moments for the fluctuation-driven event-by-event v2 distribution are determined, including the skewness, kurtosis and, for the first time, superskewness. Assuming a hydrodynamic expansion of the produced medium, these moments directly probe the initial-state geometry in high-energy nucleus-nucleus collisions. © The Author(s) 2024.Öğe Measurement of the electroweak production of Formula Presented in association with two jets in proton-proton collisions at Formula Presented(American Physical Society, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.A measurement is presented for the electroweak production of a Formula Presented boson, a photon (Formula Presented), and two jets (j) in proton-proton collisions. The leptonic decay of the Formula Presented boson is selected by requiring one identified electron or muon and large missing transverse momentum. The two jets are required to have large invariant dijet mass and large separation in pseudorapidity. The measurement is performed with the data collected by the CMS detector at a center-of-mass energy of Formula Presented, corresponding to an integrated luminosity of Formula Presented. The cross section for the electroweak Formula Presented production is Formula Presented, whereas the total cross section for Formula Presented production is Formula Presented. Differential cross sections are also measured with the distributions unfolded to the particle level. All results are in agreement with the standard model expectations. Constraints are placed on anomalous quartic gauge couplings (aQGCs) in terms of dimension-8 effective field theory operators. These are the most stringent limits to date on the aQGCs parameters Formula Presented and Formula Presented. © 2023 CERN, for the CMS Collaboration.Öğe Measurement of the production cross section for a W boson in association with a charm quark in proton–proton collisions at ?s=13TeV(Springer Nature, 2024) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.The strange quark content of the proton is probed through the measurement of the production cross section for a W boson and a charm (c) quark in proton–proton collisions at a center-of-mass energy of 13 TeV . The analysis uses a data sample corresponding to a total integrated luminosity of 138 fb-1 collected with the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm jets are tagged using the presence of a muon or a secondary vertex inside the jet. The W + c production cross section and the cross section ratio Rc±=?(W++c¯)/?(W-+c) are measured inclusively and differentially as functions of the transverse momentum and the pseudorapidity of the lepton originating from the W boson decay. The precision of the measurements is improved with respect to previous studies, reaching 1% in Rc±=0.950±0.005(stat)±0.010(syst) . The measurements are compared with theoretical predictions up to next-to-next-to-leading order in perturbative quantum chromodynamics. © 2024, The Author(s).Öğe Measurement of the top quark mass using a profile likelihood approach with the lepton + jets final states in proton–proton collisions at ?s=13TeV(Institute for Ionics, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.The mass of the top quark is measured in 36.3 fb-1 of LHC proton–proton collision data collected with the CMS detector at s=13TeV . The measurement uses a sample of top quark pair candidate events containing one isolated electron or muon and at least four jets in the final state. For each event, the mass is reconstructed from a kinematic fit of the decay products to a top quark pair hypothesis. A profile likelihood method is applied using up to four observables per event to extract the top quark mass. The top quark mass is measured to be 171.77±0.37GeV . This approach significantly improves the precision over previous measurements. © 2023, The Author(s).Öğe Observation of Same-Sign WW Production from Double Parton Scattering in Proton-Proton Collisions at Formula Presented(American Physical Society, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.The first observation of the production of Formula Presented bosons from double parton scattering processes using same-sign electron-muon and dimuon events in proton-proton collisions is reported. The data sample corresponds to an integrated luminosity of Formula Presented recorded at a center-of-mass energy of 13 TeV using the CMS detector at the CERN LHC. Multivariate discriminants are used to distinguish the signal process from the main backgrounds. A binned maximum likelihood fit is performed to extract the signal cross section. The measured cross section for production of same-sign Formula Presented bosons decaying leptonically is Formula Presented, whereas the measured fiducial cross section is Formula Presented. The observed significance of the signal is 6.2 standard deviations above the background-only hypothesis. © 2023 CERN, for the CMS Collaboration.Öğe A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer(Springer Nature, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.A generic search is presented for the associated production of a Z boson or a photon with an additional unspecified massive particle X, pp ? pp + Z / ? + X , in proton-tagged events from proton–proton collisions at s=13TeV , recorded in 2017 with the CMS detector and the CMS-TOTEM precision proton spectrometer. The missing mass spectrum is analysed in the 600–1600 GeV range and a fit is performed to search for possible deviations from the background expectation. No significant excess in data with respect to the background predictions has been observed. Model-independent upper limits on the visible production cross section of pp ? pp + Z / ? + X are set. © 2023, The Author(s).Öğe Search for nonresonant Higgs boson pair production in the four leptons plus twob jets final state in proton-proton collisions at ?s = 13 TeV(Springer Science and Business Media Deutschland GmbH, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.The first search for nonresonant production of Higgs boson pairs (HH) with one H decaying into four leptons and the other into a pair of b quarks is presented, using proton-proton collisions recorded at a center-of-mass energy of s = 13 TeV by the CMS experiment. The analyzed data correspond to an integrated luminosity of 138 fb?1. A 95% confidence level upper limit of 32.4 is set on the signal strength modifier ?, defined as the ratio of the observed HH production rate in the HH? ZZ?b b ¯ ? 4 ?b b ¯ decay channel to the standard model (SM) expectation. Possible modifications of the H trilinear coupling ? HHH with respect to the SM value are investigated. The coupling modifier ??, defined as ? HHH divided by its SM prediction, is constrained to be within the observed (expected) range ?8.8 (?9.8) < ?? < 13.4 (15.0) at 95% confidence level. [Figure not available: see fulltext.]. © 2023, The Author(s).Öğe Search for top squarks in the four-body decay mode with single lepton final states in proton-proton collisions at ?s = 13 TeV(Springer Science and Business Media Deutschland GmbH, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.A search for the pair production of the lightest supersymmetric partner of the top quark, the top squark (t ~1), is presented. The search targets the four-body decay of the 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 (?~10), 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(t ~1) and m(?~10). 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(t ~1) ? m(?~10) = 10 and 80 GeV, respectively. [Figure not available: see fulltext.]. © 2023, The Author(s).
