Rectorate / Rektörlük
Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
Browse
4 results
Search Results
Article Citation - WoS: 15Citation - Scopus: 19Study of J/Ψ Meson Production Inside Jets in pp Collisions at S=8 TeV(Elsevier B.V., 2020) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Bergauer, T.; Brandstetter, J.; Hensel, C.A study of the production of prompt J/ψ mesons contained in jets in proton-proton collisions at s=8TeV is presented. The analysis is based on data corresponding to an integrated luminosity of 19.1 fb−1 collected with the CMS detector at the LHC. For events with at least one observed jet, the angular separation between the J/ψ meson and the jet is used to test whether the J/ψ meson is part of the jet. The analysis shows that most prompt J/ψ mesons having energy above 15 GeV and rapidity |y|<1 are contained in jets with pseudorapidity |η<inf>jet</inf>|<1. The differential distributions of the probability to have a J/ψ meson contained in a jet as a function of jet energy for a fixed J/ψ energy fraction are compared to a theoretical model using the fragmenting jet function approach. The data agree best with fragmenting jet function calculations that use a long-distance matrix element parameter set in which prompt J/ψ mesons are predicted to be unpolarized. This technique demonstrates a new way to test predictions for prompt J/ψ production using nonrelativistic quantum chromodynamics. © 2020 Elsevier B.V.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: 32Citation - Scopus: 49Measurement of the tt‾bb‾ Production Cross Section in the All-Jet Final State in pp Collisions at S=13 TeV(Elsevier B.V., 2020) Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Bergauer, T.; Brandstetter, J.; Moraes, A.A measurement of the production cross section of top quark pairs in association with two b jets (tt‾bb‾) is presented using data collected in proton-proton collisions at s=13 TeV by the CMS detector at the LHC corresponding to an integrated luminosity of 35.9 fb−1. The cross section is measured in the all-jet decay channel of the top quark pair by selecting events containing at least eight jets, of which at least two are identified as originating from the hadronization of b quarks. A combination of multivariate analysis techniques is used to reduce the large background from multijet events not containing a top quark pair, and to help discriminate between jets originating from top quark decays and other additional jets. The cross section is determined for the total phase space to be 5.5±0.3(stat)<inf>−1.3</inf> +1.6(syst)pb and also measured for two fiducial tt‾bb‾ definitions. The measured cross sections are found to be larger than theoretical predictions by a factor of 1.5–2.4, corresponding to 1–2 standard deviations. © 2020 The Author