PubMed İndeksli Yayınlar Koleksiyonu / PubMed Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7645
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Article Citation - WoS: 30Citation - Scopus: 56Observation of Top Quark Production in Proton-Nucleus Collisions(American Physical Society, 2017) CMS Collaboration; Karapınar, GülerThe first observation of top quark production in proton-nucleus collisions is reported using proton-lead data collected by the CMS experiment at the CERN LHC at a nucleon-nucleon center-of-mass energy of sNN=8.16 TeV. The measurement is performed using events with exactly one isolated electron or muon candidate and at least four jets. The data sample corresponds to an integrated luminosity of 174 nb-1. The significance of the tt signal against the background-only hypothesis is above 5 standard deviations. The measured cross section is σtt=45±8 nb, consistent with predictions from perturbative quantum chromodynamics.Article Citation - WoS: 22Citation - Scopus: 44Search for Evidence of the Type-Iii Seesaw Mechanism in Multilepton Final States in Proton-Proton Collisions at ?s =13 Tev(American Physical Society, 2017) CMS Collaboration; Karapınar, GülerA search for a signal consistent with the type-III seesaw mechanism in events with three or more electrons or muons is presented. The data sample consists of proton-proton collisions at s=13 TeV collected by the CMS experiment at the LHC in 2016 and corresponds to an integrated luminosity of 35.9 fb-1. Selection criteria based on the number of leptons and the invariant mass of oppositely charged lepton pairs are used to distinguish the signal from the standard model background. The observations are consistent with the expectations from standard model processes. The results are used to place limits on the production of heavy fermions of the type-III seesaw model as a function of the branching ratio to each lepton flavor. In the scenario of equal branching fractions to each lepton flavor, heavy fermions with masses below 840 GeV are excluded. This is the most sensitive probe to date of the type-III seesaw mechanism.Article Citation - WoS: 61Citation - Scopus: 111Measurement of the B± Meson Nuclear Modification Factor in Pb-Pb Collisions at ??snn =5.02 Tev(American Physical Society, 2017) CMS Collaboration; Karapınar, GülerThe differential production cross sections of B± mesons are measured via the exclusive decay channels B±→J/ψK±→μ+μ-K± as a function of transverse momentum in pp and Pb-Pb collisions at a center-of-mass energy sNN=5.02 TeV per nucleon pair with the CMS detector at the LHC. The pp(Pb-Pb) data set used for this analysis corresponds to an integrated luminosity of 28.0 pb-1 (351 μb-1). The measurement is performed in the B± meson transverse momentum range of 7 to 50 GeV/c, in the rapidity interval |y|<2.4. In this kinematic range, a strong suppression of the production cross section by about a factor of 2 is observed in the Pb-Pb system in comparison to the expectation from pp reference data. These results are found to be roughly compatible with theoretical calculations incorporating beauty quark diffusion and energy loss in a quark-gluon plasma.Article Citation - WoS: 41Citation - Scopus: 71Search for Charged Higgs Bosons Produced Via Vector Boson Fusion and Decaying Into a Pair of W and Z Bosons Using Pp Collisions at ?s =13 Tev(American Physical Society, 2017) CMS Collaboration; Karapınar, GülerA search for charged Higgs bosons produced via vector boson fusion and decaying into W and Z bosons using proton-proton collisions at s=13 TeV is presented. The data sample corresponds to an integrated luminosity of 15.2 fb-1 collected with the CMS detector in 2015 and 2016. The event selection requires three leptons (electrons or muons), two jets with large pseudorapidity separation and high dijet mass, and missing transverse momentum. The observation agrees with the standard model prediction. Limits on the vector boson fusion production cross section times branching fraction for new charged physical states are reported as a function of mass from 200 to 2000 GeV and interpreted in the context of Higgs triplet models.Article Citation - WoS: 14Citation - Scopus: 38Search for Low Mass Vector Resonances Decaying To Quark-Antiquark Pairs in Proton-Proton Collisions at √s =13 Tev(American Physical Society, 2017) CMS Collaboration; Karapınar, GülerA search is reported for a narrow vector resonance decaying to quark-antiquark pairs in proton-proton collisions at s=13 TeV, collected with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.7 fb-1. The vector resonance is produced at large transverse momenta, with its decay products merged into a single jet. The resulting signature is a peak over background in the distribution of the invariant mass of the jet. The results are interpreted in the framework of a leptophobic vector resonance and no evidence is found for such particles in the mass range of 100-300 GeV. Upper limits at 95% confidence level on the production cross section are presented in a region of mass-coupling phase space previously unexplored at the LHC. The region below 140 GeV has not been explored by any previous experiments.Article Citation - WoS: 32Citation - Scopus: 67Study of Jet Quenching With Z+jet Correlations in Pb-Pb and Pp Collisions at S Nn=5.02 Tev(American Physical Society, 2017) CMS Collaboration; Karapınar, GülerThe production of jets in association with Z bosons, reconstructed via the μ+μ- and e+e- decay channels, is studied in pp and, for the first time, in Pb-Pb collisions. Both data samples were collected by the CMS experiment at the LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The Pb-Pb collisions were analyzed in the 0%-30% centrality range. The back-to-back azimuthal alignment was studied in both pp and Pb-Pb collisions for Z bosons with transverse momentum pTZ>60 GeV/c and a recoiling jet with pTjet>30 GeV/c. The pT imbalance xjZ=pTjet/pTZ, as well as the average number of jet partners per Z, RjZ, was studied in intervals of pTZ. The RjZ is found to be smaller in Pb-Pb than in pp collisions, which suggests that in Pb-Pb collisions a larger fraction of partons associated with the Z bosons fall below the 30 GeV/c pTjet threshold because they lose energy.Article Citation - WoS: 22Citation - Scopus: 38Relative Modification of Prompt ? (2s) and J /? Yields From Pp To Pbpb Collisions at Snn =5.02 Tev(American Physical Society, 2017) CMS Collaboration; Karapınar, GülerThe relative modification of the prompt ψ(2S) and J/ψ yields from pp to PbPb collisions, at the center-of-mass energy of 5.02 TeV per nucleon pair, is presented. The analysis is based on pp and PbPb data samples collected by the CMS experiment at the LHC in 2015, corresponding to integrated luminosities of 28.0 pb-1 and 464 μb-1, respectively. The double ratio of measured yields of prompt charmonia reconstructed through their decays into muon pairs, (Nψ(2S)/NJ/ψ)PbPb/(Nψ(2S)/NJ/ψ)pp, is determined as a function of PbPb collision centrality and charmonium transverse momentum pT, in two kinematic intervals: |y|<1.6 covering 6.5<pT<30 GeV/c and 1.6<|y|<2.4 covering 3<pT<30 GeV/c. The centrality-integrated double ratios are 0.36±0.08(stat)±0.05(syst) in the first interval and 0.24±0.22(stat)±0.09(syst) in the second. The double ratio is lower than unity in all the measured bins, suggesting that the ψ(2S) yield is more suppressed than the J/ψ yield in the explored phase space. © 2017 CERN.Article Citation - WoS: 118Citation - Scopus: 138Observation of Charge-Dependent Azimuthal Correlations in P-Pb Collisions and Its Implication for the Search for the Chiral Magnetic Effect(American Physical Society, 2017) CMS Collaboration; Karapınar, GülerCharge-dependent azimuthal particle correlations with respect to the second-order event plane in p-Pb and PbPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV have been studied with the CMS experiment at the LHC. The measurement is performed with a three-particle correlation technique, using two particles with the same or opposite charge within the pseudorapidity range |η|<2.4, and a third particle measured in the hadron forward calorimeters (4.4<|η|<5). The observed differences between the same and opposite sign correlations, as functions of multiplicity and η gap between the two charged particles, are of similar magnitude in p-Pb and PbPb collisions at the same multiplicities. These results pose a challenge for the interpretation of charge-dependent azimuthal correlations in heavy ion collisions in terms of the chiral magnetic effect.Article Citation - WoS: 22Citation - Scopus: 27Search for Dark Matter and Supersymmetry With a Compressed Mass Spectrum in the Vector Boson Fusion Topology in Proton-Proton Collisions at ?s =8 Tev(American Physical Society, 2017) CMS Collaboration; Karapınar, GülerA first search for pair production of dark matter candidates through vector boson fusion in proton-proton collisions at s=8 TeV is performed with the CMS detector. The vector boson fusion topology enhances missing transverse momentum, providing a way to probe supersymmetry, even in the case of a compressed mass spectrum. The data sample corresponds to an integrated luminosity of 18.5 fb-1, recorded by the CMS experiment. The observed dijet mass spectrum is consistent with the standard model expectation. In an effective field theory, dark matter masses are explored as a function of contact interaction strength. The most stringent limit on bottom squark production with mass below 315 GeV is also reported, assuming a 5 GeV mass difference with respect to the lightest neutralino.Article Citation - WoS: 44Citation - Scopus: 40Measurements of the Tt¯ Production Cross Section in Lepton+jets Final States in Pp Collisions at 8 Tev and Ratio of 8 To 7 Tev Cross Sections(Springer Verlag, 2017) CMS Collaboration; Karapınar, GülerA measurement of the top quark pair production (tt¯) cross section in proton–proton collisions at the centre-of-mass energy of 8TeV is presented using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.6fb-1. This analysis is performed in the tt¯ decay channels with one isolated, high transverse momentum electron or muon and at least four jets, at least one of which is required to be identified as originating from hadronization of a b quark. The calibration of the jet energy scale and the efficiency of b jet identification are determined from data. The measured tt¯ cross section is 228.5±3.8(stat)±13.7(syst)±6.0(lumi) pb. This measurement is compared with an analysis of 7TeV data, corresponding to an integrated luminosity of 5.0fb-1, to determine the ratio of 8TeV to 7TeV cross sections, which is found to be 1.43±0.04(stat)±0.07(syst)±0.05(lumi). The measurements are in agreement with QCD predictions up to next-to-next-to-leading order.
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