Rectorate / Rektörlük
Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
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Article Citation - WoS: 70Citation - Scopus: 75Search for Singly and Pair-Produced Leptoquarks Coupling To Third-Generation Fermions in Proton-Proton Collisions at S=13 Tev(Elsevier B.V., 2021) Sirunyan,A.M.; Tumasyan,A.; Adam,W.; Ambrogi,F.; Bergauer,T.; Dragicevic,M.; Chistov,R.A search for leptoquarks produced singly and in pairs in proton-proton collisions is presented. We consider the leptoquark (LQ) to be a scalar particle of charge −1/3e coupling to a top quark plus a tau lepton (tτ) or a bottom quark plus a neutrino (bν), or a vector particle of charge +2/3e, coupling to tν or bτ. These choices are motivated by models that can explain a series of anomalies observed in the measurement of B meson decays. In this analysis the signatures tτνb and tτν are probed, using data recorded by the CMS experiment at the CERN LHC at s=13 TeV and that correspond to an integrated luminosity of 137 fb−1. These signatures have not been previously explored in a dedicated search. The data are found to be in agreement with the standard model prediction. Lower limits at 95% confidence level are set on the LQ mass in the range 0.98–1.73 TeV, depending on the LQ spin and its coupling λ to a lepton and a quark, and assuming equal couplings for the two LQ decay modes considered. These are the most stringent constraints to date on the existence of leptoquarks in this scenario. © 2021 The Author(s)Article Citation - WoS: 40Citation - Scopus: 57Measurements of Production Cross Sections of Polarized Same-Sign W Boson Pairs in Association With Two Jets in Proton-Proton Collisions at S=13 Tev(Elsevier B.V., 2021) Sirunyan,A.M.; Tumasyan,A.; Adam,W.; Ambrogi,F.; Bergauer,T.; Dragicevic,M.; Chistov,R.The first measurements of production cross sections of polarized same-sign W±W± boson pairs in proton-proton collisions are reported. The measurements are based on a data sample collected with the CMS detector at the LHC at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 137fb−1. Events are selected by requiring exactly two same-sign leptons, electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass to enhance the contribution of same-sign W±W± scattering events. An observed (expected) 95% confidence level upper limit of 1.17 (0.88) fbis set on the production cross section for longitudinally polarized same-sign W±W± boson pairs. The electroweak production of same-sign W±W± boson pairs with at least one of the W bosons longitudinally polarized is measured with an observed (expected) significance of 2.3 (3.1) standard deviations. © 2020 The Author(s)Article Citation - WoS: 34Citation - Scopus: 47Measurement of the Cp-Violating Phase Φs in the Bs 0→j/Ψϕ(1020)→μ+μ−k+k− Channel in Proton-Proton Collisions at S=13tev(Elsevier B.V., 2021) Sirunyan,A.M.; Tumasyan,A.; Adam,W.; Ambrogi,F.; Bergauer,T.; Dragicevic,M.; Chistov,R.The CP -violating weak phase ϕs and the decay width difference ΔΓs between the light and heavy Bs 0 mass eigenstates are measured with the CMS detector at the LHC in a sample of 48500 reconstructed Bs 0→J/ψϕ(1020)→μ+μ−K+K− events. The measurement is based on a data sample corresponding to an integrated luminosity of 96.4fb−1, collected in proton-proton collisions at s=13TeV in 2017–2018. To extract the values of ϕs and ΔΓs, a time-dependent and flavor-tagged angular analysis of the μ+μ−K+K− final state is performed. The analysis employs a dedicated tagging trigger and a novel opposite-side muon flavor tagger based on machine learning techniques. The measurement yields ϕs=−11±50(stat)±10(syst)mrad and ΔΓs=0.114±0.014(stat)±0.007(syst)ps−1, in agreement with the standard model predictions. When combined with the previous CMS measurement at s=8TeV, the following values are obtained: ϕs=−21±44(stat)±10(syst)mrad, ΔΓs=0.1032±0.0095(stat)±0.0048(syst)ps−1, a significant improvement over the 8 TeV result. © 2021 The Author(s)Article Citation - WoS: 20Citation - Scopus: 29Measurement of the Top Quark Yukawa Coupling From Tt¯ Kinematic Distributions in the Dilepton Final State in Proton-Proton Collisions at S=13 Tev(American Physical Society, 2020) Sirunyan,A.M.; Tumasyan,A.; Adam,W.; Ambrogi,F.; Bergauer,T.; Dragicevic,M.; Chistov,R.A measurement of the Higgs boson Yukawa coupling to the top quark is presented using proton-proton collision data at s=13 TeV, corresponding to an integrated luminosity of 137 fb-1, recorded with the CMS detector. The coupling strength with respect to the standard model value, Yt, is determined from kinematic distributions in tt¯ final states containing ee, μμ, or eμ pairs. Variations of the Yukawa coupling strength lead to modified distributions for tt¯ production. In particular, the distributions of the mass of the tt¯ system and the rapidity difference of the top quark and antiquark are sensitive to the value of Yt. The measurement yields a best fit value of Yt=1.16-0.35+0.24, bounding Yt<1.54 at a 95% confidence level. © 2020 CERN.