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Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
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Article Citation - WoS: 29Citation - Scopus: 33Measurement of the Jet Mass in Highly Boosted T T ¯ Events From Pp Collisions at √s=8tev(Springer Nature, 2017) Sirunyan, A.M.; Karapınar, Güler; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Baillon, P.The first measurement of the jet mass mjet of top quark jets produced in t t ¯ events from pp collisions at s=8TeV is reported for the jet with the largest transverse momentum pT in highly boosted hadronic top quark decays. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 19.7fb-1. The measurement is performed in the lepton+jets channel in which the products of the semileptonic decay t → b W with W → ℓν where ℓ is an electron or muon, are used to select t t ¯ events with large Lorentz boosts. The products of the fully hadronic decay t → b W with W → q q ¯ ′ are reconstructed using a single Cambridge–Aachen jet with distance parameter R= 1.2 , and pT> 400 GeV. The t t ¯ cross section as a function of mjet is unfolded at the particle level and is used to test the modelling of highly boosted top quark production. The peak position of the mjet distribution is sensitive to the top quark mass mt, and the data are used to extract a value of mt to assess this sensitivity. © 2017, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 22Citation - Scopus: 26Search for Black Holes and Other New Phenomena in High-Multiplicity Final States in Proton-Proton Collisions at Root S=13 Tev(Elsevier Ltd., 2017) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Karapınar, Güler; CMS CollaborationA search for new physics in energetic, high-multiplicity final states has been performed using proton-proton collision data collected with the CMS detector at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 2.3 fb(-1). The standard model background, dominated by multijet production, is determined exclusively from control regions in data. No statistically significant excess of events is observed. Model-independent limits on the product of the cross section and the acceptance of a new physics signal in these final states are set and further interpreted in terms of limits on the production of black holes. Semiclassical black holes and string balls with masses as high as 9.5 TeV, and quantum black holes with masses as high as 9.0 TeV are excluded by this search in the context of models with extra dimensions, thus significantly extending limits set at a center-of-mass energy of 8 TeV with the LHC Run 1 data. (c) 2017 The Author(s). Published by Elsevier B.V.Article Citation - WoS: 24Citation - Scopus: 27Search for Supersymmetry With Higgs Boson To Diphoton Decays Using the Razor Variables at Root S=13 Tev(Elsevier Ltd., 2018) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Karapınar, Güler; CMS CollaborationAn inclusive search for anomalous Higgs boson production in the diphoton decay channel and in association with at least one jet is presented, using LHC proton-proton collision data collected by the CMS experiment at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 35.9 fb(-1). The razor variables M-R and R-2, as well as the momentum and mass resolution of the diphoton system, are used to categorize events into different search regions. The search result is interpreted in the context of strong and electroweak production of supersymmetric particles. We exclude bottom squark pair-production with masses below 450 GeV for bottom squarks decaying to a bottom quark, a Higgs boson, and the lightest supersymmetric particle (LSP) for LSP masses below 250 GeV. For wino-like chargino-neutralino production, we exclude charginos with mass below 170 GeV for LSP masses below 25 GeV. In the GMSB scenario, we exclude charginos with mass below 205 GeV for neutralinos decaying to a Higgs boson and a goldstino LSP with 100% branching fraction. C) 2018 The Author(s). Published by Elsevier B.V.Article Citation - WoS: 84Citation - Scopus: 96Search for Supersymmetric Partners of Electrons and Muons in Proton–proton Collisions at S=13tev(Elsevier B.V., 2019) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Slabospitskii, S.A search for direct production of the supersymmetric (SUSY) partners of electrons or muons is presented in final states with two opposite-charge, same-flavour leptons (electrons and muons), no jets, and large missing transverse momentum. The data sample corresponds to an integrated luminosity of 35.9 fb−1 of proton–proton collisions at s=13TeV, collected with the CMS detector at the LHC in 2016. The search uses the MT2 variable, which generalises the transverse mass for systems with two invisible objects and provides a discrimination against standard model backgrounds containing W bosons. The observed yields are consistent with the expectations from the standard model. The search is interpreted in the context of simplified SUSY models and probes slepton masses up to approximately 290, 400, and 450 GeV, assuming right-handed only, left-handed only, and both right- and left-handed sleptons (mass degenerate selectrons and smuons), and a massless lightest supersymmetric particle. Limits are also set on selectrons and smuons separately. These limits show an improvement on the existing limits of approximately 150 GeV. © 2019 The Author(s)Article Citation - WoS: 38Citation - Scopus: 43Observation of Prompt J/Ψ Meson Elliptic Flow in High-Multiplicity Ppb Collisions at √snn=8.16 Tev(Elsevier B.V., 2019) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Petrov, V.A measurement of the elliptic flow (v2) of prompt J/ψ mesons in high-multiplicity pPb collisions is reported using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy sNN=8.16TeV. Prompt J/ψ mesons decaying into two muons are reconstructed in the rapidity region in the nucleon-nucleon center-of-mass frame (ycm), corresponding to either −2.86<ycm<−1.86 or 0.94<ycm<1.94. The average v2 result from the two rapidity ranges is reported over the transverse momentum (pT) range from 0.2 to 10 GeV. Positive v2 values are observed for the prompt J/ψ meson, as extracted from long-range two-particle correlations with charged hadrons, for 2<pT<8 GeV. The prompt J/ψ results are compared with previous CMS measurements of elliptic flow for open charm mesons (D0) and strange hadrons. From these measurements, constraints can be obtained on the collective dynamics of charm quarks produced in high-multiplicity events arising from small systems. © 2019 The Author(s)Article Citation - WoS: 92Citation - Scopus: 106Search for an Lμ − Lτ gauge boson using Z → 4μ events in proton-proton collisions at s=13 TeV(Elsevier B.V., 2019) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Konstantinov, D.A search for a narrow Z′ gauge boson with a mass between 5 and 70 GeV resulting from an Lμ−Lτ U(1) local gauge symmetry is reported. Theories that predict such a particle have been proposed as an explanation of various experimental discrepancies, including the lack of a dark matter signal in direct-detection experiments, tension in the measurement of the anomalous magnetic moment of the muon, and reports of possible lepton flavor universality violation in B meson decays. A data sample of proton-proton collisions at a center-of-mass energy of 13 TeV is used, corresponding to an integrated luminosity of 77.3 fb−1 recorded in 2016 and 2017 by the CMS detector at the LHC. Events containing four muons with an invariant mass near the standard model Z boson mass are analyzed, and the selection is further optimized to be sensitive to the events that may contain Z→Z′μμ→4μ decays. The event yields are consistent with the standard model predictions. Upper limits of 10−8–10−7 at 95% confidence level are set on the product of branching fractions B(Z→Z′μμ)B(Z′→μμ), depending on the Z′ mass, which excludes a Z′ boson coupling strength to muons above 0.004–0.3. These are the first dedicated limits on Lμ−Lτ models at the LHC and result in a significant increase in the excluded model parameter space. The results of this search may also be used to constrain the coupling strength of any light Z′ gauge boson to muons. © 2019 The Author(s)Article Citation - WoS: 30Measurement of the Single Top Quark and Antiquark Production Cross Sections in the T Channel and Their Ratio in Proton-Proton Collisions at Root S=13 Tev(Elsevier Ltd., 2020) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Karapınar, Güler; CMS CollaborationMeasurements of the cross sections for the production of single top quarks and antiquarks in the t channel, and their ratio, are presented for proton-proton collisions at a center-of-mass energy of 13 TeV. The data set used was recorded in 2016 by the CMS detector at the LHC and corresponds to an integrated luminosity of 35.9 fb(-1). Events with one muon or electron are selected, and different categories of jet and b jet multiplicity and multivariate discriminators are applied to separate the signal from the background. The cross sections for the t-channel production of single top quarks and antiquarks are measured to be 130 +/- 1(stat) +/- 19(syst) pb and 77 +/- 1(stat) +/- 12(syst) pb, respectively, and their ratio is 1.68 +/- 0.02(stat) +/- 0.05(syst). The results are in agreement with the predictions from the standard model. (C) 2019 The Author(s). Published by Elsevier B.V.Article Citation - WoS: 30Citation - Scopus: 40Observation of Nuclear Modifications in W± Boson Production in Ppb Collisions at Snn=8.16tev(Elsevier B.V., 2020) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Sobol, A.The production of W± bosons is studied in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of sNN=8.16TeV. Measurements are performed in the W±→μ±νμ channel using a data sample corresponding to an integrated luminosity of 173.4±6.1nb−1, collected by the CMS Collaboration at the LHC. The number of positively and negatively charged W bosons is determined separately in the muon pseudorapidity region in the laboratory frame |ηlab μ|<2.4 and transverse momentum pT μ>25GeV/c. The W± boson differential cross sections, muon charge asymmetry, and the ratios of W± boson yields for the proton-going over the Pb-going beam directions are reported as a function of the muon pseudorapidity in the nucleon-nucleon centre-of-mass frame. The measurements are compared to the predictions from theoretical calculations based on parton distribution functions (PDFs) at next-to-leading-order. The results favour PDF calculations that include nuclear modifications and provide constraints on the nuclear PDF global fits. © 2019 The Author(s)