Rectorate / Rektörlük
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Article Citation - WoS: 205Citation - Scopus: 159Search for Resonances and Quantum Black Holes Using Dijet Mass Spectra in Proton-Proton Collisions at S =8tev(American Physical Society, 2015) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; Hegeman, J.A search for resonances and quantum black holes is performed using the dijet mass spectra measured in proton-proton collisions at s=8TeV with the CMS detector at the LHC. The data set corresponds to an integrated luminosity of 19.7fb-1. In a search for narrow resonances that couple to quark-quark, quark-gluon, or gluon-gluon pairs, model-independent upper limits, at 95% confidence level, are obtained on the production cross section of resonances, with masses above 1.2 TeV. When interpreted in the context of specific models the limits exclude string resonances with masses below 5.0 TeV; excited quarks below 3.5 TeV; scalar diquarks below 4.7 TeV; W′ bosons below 1.9 TeV or between 2.0 and 2.2 TeV; Z′ bosons below 1.7 TeV; and Randall-Sundrum gravitons below 1.6 TeV. A separate search is conducted for narrow resonances that decay to final states including b quarks. The first exclusion limit is set for excited b quarks, with a lower mass limit between 1.2 and 1.6 TeV depending on their decay properties. Searches are also carried out for wide resonances, assuming for the first time width-to-mass ratios up to 30%, and for quantum black holes with a range of model parameters. The wide resonance search excludes axigluons and colorons with mass below 3.6 TeV, and color-octet scalars with mass below 2.5 TeV. Lower bounds between 5.0 and 6.3 TeV are set on the masses of quantum black holes. © 2015 CERN, for the CMS Collaboration.Article Citation - WoS: 1Citation - Scopus: 6Search for Supersymmetry With Photons in Pp Collisions at S =8tev(American Physical Society, 2015) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Calvo, E.Two searches for physics beyond the standard model in events containing photons are presented. The data sample used corresponds to an integrated luminosity of 19.7fb-1 of proton-proton collisions at s=8TeV, collected with the CMS experiment at the CERN LHC. The analyses pursue different inclusive search strategies. One analysis requires at least one photon, at least two jets, and a large amount of transverse momentum imbalance, while the other selects events with at least two photons and at least one jet, and uses the razor variables to search for signal events. The background expected from standard model processes is evaluated mainly from data. The results are interpreted in the context of general gauge-mediated supersymmetry, with the next-to-lightest supersymmetric particle either a bino- or wino-like neutralino, and within simplified model scenarios. Upper limits at the 95% confidence level are obtained for cross sections as functions of the masses of the intermediate supersymmetric particles. © 2015 CERN. © 2015 CERN, for the CMS Collaboration. Published by the American Physical Society under the terms of the "http://creativecommons.org/licenses/by/3.0/" Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Article Citation - WoS: 65Citation - Scopus: 62Search for the standard model Higgs boson produced through vector boson fusion and decaying to b¯b(American Physical Society, 2015) CMS Collaboration; Karapınar, GülerA first search is reported for a standard model Higgs boson (H) that is produced through vector boson fusion and decays to a bottom-quark pair. Two data samples, corresponding to integrated luminosities of 19.8fb-1 and 18.3fb-1 of proton-proton collisions at s=8TeV were selected for this channel at the CERN LHC. The observed significance in these data samples for a H→bb¯ signal at a mass of 125 GeV is 2.2 standard deviations, while the expected significance is 0.8 standard deviations. The fitted signal strength μ=σ/σSM=2.8-1.4+1.6. The combination of this result with other CMS searches for the Higgs boson decaying to a b-quark pair yields a signal strength of 1.0±0.4, corresponding to a signal significance of 2.6 standard deviations for a Higgs boson mass of 125 GeV. © 2015 CERN.Article Citation - WoS: 48Citation - Scopus: 69Limits on the Higgs Boson Lifetime and Width From Its Decay To Four Charged Leptons(American Physical Society, 2015) Khachatryan, V.; Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Asilar, E.; Soares, M.S.Constraints on the lifetime and width of the Higgs boson are obtained from H→ZZ→4ℓ events using data recorded by the CMS experiment during the LHC run 1 with an integrated luminosity of 5.1 and 19.7fb-1 at a center-of-mass energy of 7 and 8 TeV, respectively. The measurement of the Higgs boson lifetime is derived from its flight distance in the CMS detector with an upper bound of τH<1.9×10-13s at the 95% confidence level (C.L.), corresponding to a lower bound on the width of ΓH>3.5×10-9MeV. The measurement of the width is obtained from an off-shell production technique, generalized to include anomalous couplings of the Higgs boson to two electroweak bosons. From this measurement, a joint constraint is set on the Higgs boson width and a parameter fΛQ that expresses an anomalous coupling contribution as an on-shell cross-section fraction. The limit on the Higgs boson width is ΓH<46MeV with fΛQ unconstrained and ΓH<26MeV for fΛQ=0 at the 95% C.L. The constraint fΛQ<3.8×10-3 at the 95% C.L. is obtained for the expected standard model Higgs boson width. © 2015 CERN, for the CMS. Published by the American Physical Society.Article Citation - WoS: 5Citation - Scopus: 6Production of Leading Charged Particles and Leading Charged-Particle Jets at Small Transverse Momenta in Pp Collisions at Sqrt(s) = 8 Tev(American Physical Society, 2015) CMS Collaboration; Karapınar, GülerThe per-event yield of the highest transverse momentum charged particle and charged-particle jet, integrated above a given pTmin threshold starting at pTmin=0.8 and 1 GeV, respectively, is studied in pp collisions at s=8 TeV. The particles and the jets are measured in the pseudorapidity ranges |η|<2.4 and 1.9, respectively. The data are sensitive to the momentum scale at which parton densities saturate in the proton, to multiple partonic interactions, and to other key aspects of the transition between the soft and hard QCD regimes in hadronic collisions. © 2015 CERN, for the CMS Collaboration. Published by the American Physical Society under the terms of the »http://creativecommons.org/licenses/by/3.0/» Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Article Citation - WoS: 22Citation - Scopus: 38Combined Search for the Quarks of a Sequential Fourth Generation(American Physical Society, 2012) CMS Collaboration; Karapınar, GülerResults are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5fb-1 recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about ±20GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions. © 2012 CERN.Article Citation - WoS: 20Citation - Scopus: 45Search for Pair Production of First- and Second-Generation Scalar Leptoquarks in Pp Collisions at ?s=7tev(American Physical Society, 2012) CMS Collaboration; Karapınar, GülerResults are presented from a search for the pair production of first- and second-generation scalar leptoquarks in proton-proton collisions at √s=7TeV. The data sample corresponds to an integrated luminosity of 5.0fb -1, collected by the CMS detector at the LHC. The search signatures involve either two charged leptons of the same flavor (electrons or muons) and at least two jets or a single charged lepton (electron or muon), missing transverse energy, and at least two jets. If the branching fraction of the leptoquark decay into a charged lepton and a quark is assumed to be β=1, leptoquark pair production is excluded at the 95% confidence level for masses below 830 GeV and 840 GeV for the first and second generations, respectively. For β=0.5, masses below 640 GeV and 650 GeV are excluded. These limits are the most stringent to date. © 2012 CERN.Article Citation - WoS: 23Citation - Scopus: 24Signals of Doubly-Charged Higgsinos at the Cern Large Hadron Collider(American Physical Society, 2008) Demir, Durmuş Ali; Frank, Mariana; Huitu, Katri; Rai, Santosh Kumar; Turan, İsmailSeveral supersymmetric models with extended gauge structures, motivated by either grand unification or by neutrino mass generation, predict light doubly-charged Higgsinos. In this work we study productions and decays of doubly-charged Higgsinos present in left-right supersymmetric models, and show that they invariably lead to novel collider signals not found in the minimal supersymmetric model or in any of its extensions motivated by the μ problem or even in extra dimensional theories. We investigate their distinctive signatures at the Large Hadron Collider in both pair- and single-production modes, and show that they are powerful tools in determining the underlying model via the measurements at the Large Hadron Collider experiments. © 2008 The American Physical Society