Rectorate / Rektörlük
Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
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Article Citation - WoS: 96First Measurement of the Cross Section for Top-Quark Pair Production in Proton-Proton Collisions at Root S=7 Tev(Elsevier Ltd., 2011) Karapınar, GülerThe first measurement of the cross section for top-quark pair production in pp collisions at the Large Hadron Collider at center-of-mass energy root s = 7 TeV has been performed using a data sample corresponding to an integrated luminosity of 3.1 +/- 0.3 pb(-1) recorded by the CMS detector. This result utilizes the final state with two isolated, highly energetic charged leptons, large missing transverse energy, and two or more jets. Backgrounds from Drell-Yan and non-W/Z boson production are estimated from data. Eleven events are observed in the data with 2.1 +/- 1.0 events expected from background. The measured cross section is 194 +/- 72(stat.) +/- 24(syst.) +/- 21(lumi.) pb, consistent with next-to-leading order predictions. (C) 2010 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 28Search for a W ' Boson Decaying To a Muon and a Neutrino in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2011) Karapınar, GülerA new heavy gauge boson, W', decaying to a muon and a neutrino, is searched for in pp collisions at a centre-of-mass energy of 7 TeV. The data, collected with the CMS detector at the LHC, correspond to an integrated luminosity of 36 pb(-1). No significant excess of events above the standard model expectation is found in the transverse mass distribution of the muon-neutrino system. Masses below 1.40 TeV are excluded at the 95% confidence level for a sequential standard-model-like W'. The W' mass lower limit increases to 1.58 TeV when the present analysis is combined with the CMS result for the electron channel. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 52Measurement of W Gamma and Z Gamma Production in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2011) Karapınar, GülerA measurement of W gamma and Z gamma production in proton-proton collisions at root s = 7 TeV is presented. Results are based on a data sample recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 36 pb(-1). The electron and muon decay channels of the W and Z are used. The total cross sections are measured for photon transverse energy E-T(gamma) > 10 GeV and spatial separation from charged leptons in the plane of pseudorapidity and azimuthal angle Delta R(l.gamma) > 0.7, and with an additional dilepton invariant mass requirement of M-ll > 50 GeV for the Z gamma process. The following cross section times branching fraction values are found: sigma(pp -> W gamma + X) x B(W -> lv) = 56.3 +/- 5.0(stat.) +/- 5.0(syst.) +/- 2.3(lumi.) pb and sigma(pp -> Z gamma + X) x B(Z -> ll) = 9.4 +/- 1.0(stat.) +/- 0.6(syst.) +/- 0.4(lumi.) pb. These measurements are in agreement with standard model predictions. The first limits on anomalous WW gamma, ZZ gamma, and Z gamma gamma trilinear gauge couplings at root s = 7 TeV are set. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 16Search for First Generation Scalar Leptoquarks in the E Nu Jj Channel in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2011) Karapınar, GülerA search for pair-production of first generation scalar leptoquarks is performed in the final state containing an electron, a neutrino, and at least two jets using proton-proton collision data at root s = 7 TeV. The data were collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 36 pb(-1). The number of observed events is in good agreement with the predictions for standard model processes. Prior CMS results in the dielectron channel are combined with this electron + neutrino search. A 95% confidence level combined lower limit is set on the mass of a first generation scalar leptoquark at 339 GeV for beta = 0.5, where beta is the branching fraction of the leptoquark to an electron and a quark. These results represent the most stringent direct limits to date for values of beta greater than 0.05. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 157Search for Resonances in the Dijet Mass Spectrum From 7 Tev Pp Collisions at Cms(Elsevier Ltd., 2011) Karapınar, GülerA search for narrow resonances with a mass of at least 1 TeV in the dijet mass spectrum is performed using pp collisions at root s = 7 TeV corresponding to an integrated luminosity of 1 fb(-1), collected by the CMS experiment at the LHC. No resonances are observed. Upper limits at the 95% confidence level are presented on the product of the resonance cross section, branching fraction into dijets, and acceptance, separately for decays into quark-quark, quark-gluon, and gluon-gluon pairs. The data exclude new particles predicted in the following models at the 95% confidence level: string resonances with mass less than 4.00 TeV, E-6 diquarks with mass less than 3.52 TeV, excited quarks with mass less than 2.49 TeV, axigluons and colorons with mass less than 2.47 TeV, and W' bosons with mass less than 1.51 TeV. These results extend previous exclusions from the dijet mass search technique. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 4341Observation of a New Boson at a Mass of 125 Gev With the Cms Experiment at the Lhc(Elsevier Ltd., 2012) Karapınar, GülerResults are presented from searches for the standard model Higgs boson in proton-proton collisions at root s = 7 and 8 TeV in the Compact Muon Solenoid experiment at the LHC, using data samples corresponding to integrated luminosities of up to 5.1 fb(-1) at 7 TeV and 5.3 fb(-1) at 8 TeV. The search is performed in five decay modes: gamma gamma, ZZ, W+W-, tau(+)tau(-), and b (b) over bar. An excess of events is observed above the expected background, with a local significance of 5.0 standard deviations, at a mass near 125 GeV, signalling the production of a new particle. The expected significance for a standard model Higgs boson of that mass is 5.8 standard deviations. The excess is most significant in the two decay modes with the best mass resolution, gamma gamma and ZZ; a fit to these signals gives a mass of 125.3 +/- 0.4(stat.) +/- 0.5(syst.) GeV. The decay to two photons indicates that the new particle is a boson with spin different from one. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 39Search for a W ' Boson Decaying To a Bottom Quark and a Top Quark in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2013) Karapınar, GülerResults are presented from a search for a W' boson using a dataset corresponding to 5.0 fb(-1) of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at root s=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' -> tb, leading to a final state signature with a single electron or muon, missing transverse energy, and jets, at least one of which is identified as a b-jet. A W' boson that couples to the right-handed (left-handed) chiral projections of the fermions with the same coupling constants as the W is excluded for masses below 1.85 (1.51) TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge couplings for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 26Search for Flavor Changing Neutral Currents in Top Quark Decays in Pp Collisions at 7 Tev(Elsevier Ltd., 2013) Karapınar, GülerThe results of a search for flavor changing neutral currents in top quark decays t -> Zq in events with a topology compatible with the decay chain t (t) over bar -> Wb + Zq -> lvb + llq are presented. The search is performed with a data sample corresponding to an integrated luminosity of 5.0 fb(-1) of proton-proton collisions at a center-of-mass energy of 7 TeV, collected with the CMS detector at the LHC. The observed number of events agrees with the standard model prediction and no evidence for flavor changing neutral currents in top quark decays is found. A t -> Zq branching fraction greater than 0.21% is excluded at the 95% confidence level. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 19Citation - Scopus: 20Search for Excited Leptons in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2013) Karapınar, GülerResults are presented of a search for compositeness in electrons and muons using a data sample of pp collisions at a center-of-mass energy root s = 7 TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 5.0 fb(-1). Excited leptons (l*) are assumed to be produced via contact interactions in conjunction with a standard model lepton and to decay via l* -> l gamma, yielding a final state with two energetic leptons and a photon. The number of events observed in data is consistent with that expected from the standard model. The 95% confidence upper limits for the cross section for the production and decay of excited electrons (muons), with masses ranging from 0.6 to 2 TeV, are 1.48 to 1.24 fb (1.31 to 1.11 fb). Excited leptons with masses below 1.9 TeV are excluded for the case where the contact interaction scale equals the excited lepton mass. The limits on the cross sections are the most stringent ones published to date. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 9Citation - Scopus: 9Search for Anomalous Production of Highly Boosted Z Bosons Decaying To Mu(+)mu(-) in Proton-Proton Collisions at Root S=7 Tev(Elsevier Ltd., 2013) Karapınar, GülerResults are reported from a search for the anomalous production of highly boosted Z bosons with large transverse momentum and decaying to mu(+)mu(-). Such Z bosons may be produced in the decays of new heavy particles. The search uses pp collision data at root s = 7 TeV, corresponding to an integrated luminosity of 5.0 fb(-1) recorded with the CMS detector. The shape of the observed transverse momentum distribution of Z bosons is consistent with standard model expectations. Constraints are obtained on models predicting the production of excited quarks decaying via electroweak processes. Assuming a compositeness scale that is equal to the excited quark mass as well as transition coupling strengths between Z bosons and excited quarks that are equal to standard model couplings to quarks, masses of excited quarks below 1.94 TeV are excluded at the 95% confidence level. For excited quark production via a novel contact interaction, masses below 2.22 TeV are excluded, even if the excited quarks do not couple to gluons. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved.