Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 34Citation - Scopus: 42Measurements of Tt¯ Cross Sections in Association With B Jets and Inclusive Jets and Their Ratio Using Dilepton Final States in Pp Collisions at S=13tev(Elsevier Ltd., 2018) CMS Collaboration; Karapınar, GülerThe cross sections for the production of tt¯bb¯ and tt¯jj events and their ratio σtt¯bb¯/σtt¯jj are measured using data corresponding to an integrated luminosity of 2.3 fb−1collected in pp collisions at s=13 TeV with the CMS detector at the LHC. Events with two leptons (e or μ) and at least four reconstructed jets, including at least two identified as b quark jets, in the final state are selected. In the full phase space, the measured ratio is 0.022±0.003(stat)±0.006(syst), the cross section σtt¯bb¯ is 4.0±0.6(stat)±1.3(syst) pb and σtt¯jj is 184±6(stat)±33(syst) pb. The measurements are compared with the standard model expectations obtained from a POWHEG simulation at next-to-leading-order interfaced with PYTHIA.Article Citation - WoS: 12Citation - Scopus: 16Search for a Heavy Composite Majorana Neutrino in the Final State With Two Leptons and Two Quarks at S=13tev(Elsevier Ltd., 2017) CMS Collaboration; Karapınar, GülerA search for physics beyond the standard model in the final state with two same-flavour leptons (electrons or muons) and two quarks produced in proton–proton collisions at s=13TeV is presented. The data were recorded by the CMS experiment at the CERN LHC and correspond to an integrated luminosity of 2.3fb−1. The observed data are in good agreement with the standard model background prediction. The results of the measurement are interpreted in the framework of a recently proposed model in which a heavy Majorana neutrino, Nℓ, stems from a composite-fermion scenario. Exclusion limits are set for the first time on the mass of the heavy composite Majorana neutrino, mNℓ, and the compositeness scale Λ. For the case mNℓ=Λ, the existence of Ne (Nμ) is excluded for masses up to 4.60 (4.70) TeV at 95% confidence level.Article Citation - WoS: 66Citation - Scopus: 69Constraints on Anomalous Higgs Boson Couplings Using Production and Decay Information in the Four-Lepton Final State(Elsevier Ltd., 2017) CMS Collaboration; Karapınar, GülerA search is performed for anomalous interactions of the recently discovered Higgs boson using matrix element techniques with the information from its decay to four leptons and from associated Higgs boson production with two quark jets in either vector boson fusion or associated production with a vector boson. The data were recorded by the CMS experiment at the LHC at a center-of-mass energy of 13TeV and correspond to an integrated luminosity of 38.6fb−1. They are combined with the data collected at center-of-mass energies of 7 and 8TeV, corresponding to integrated luminosities of 5.1 and 19.7fb−1, respectively. All observations are consistent with the expectations for the standard model Higgs boson.Article Citation - WoS: 70Citation - Scopus: 83Measurement of Vector Boson Scattering and Constraints on Anomalous Quartic Couplings From Events With Four Leptons and Two Jets in Proton–proton Collisions at S=13 Tev(Elsevier Ltd., 2017) CMS Collaboration; Karapınar, GülerA measurement of vector boson scattering and constraints on anomalous quartic gauge couplings from events with two Z bosons and two jets are presented. The analysis is based on a data sample of proton–proton collisions at s=13 TeV collected with the CMS detector and corresponding to an integrated luminosity of 35.9 fb−1. The search is performed in the fully leptonic final state ZZ→ℓℓℓ′ℓ′, where ℓ,ℓ′=e or μ. The electroweak production of two Z bosons in association with two jets is measured with an observed (expected) significance of 2.7 (1.6) standard deviations. A fiducial cross section for the electroweak production is measured to be σEW(pp→ZZjj→ℓℓℓ′ℓ′jj)=0.40−0.16 +0.21(stat)−0.09 +0.13(syst) fb, which is consistent with the standard model prediction. Limits on anomalous quartic gauge couplings are determined in terms of the effective field theory operators T0, T1, T2, T8, and T9. This is the first measurement of vector boson scattering in the ZZ channel at the LHC.Article Citation - WoS: 8Citation - Scopus: 9Search for Leptophobic Z' Bosons Decaying Into Four-Lepton Final States in Proton–proton Collisions at S=8tev(Elsevier Ltd., 2017) CMS Collaboration; Karapınar, GülerA search for heavy narrow resonances decaying into four-lepton final states has been performed using proton–proton collision data at s=8TeV collected by the CMS experiment, corresponding to an integrated luminosity of 19.7fb−1. No excess of events over the standard model background expectation is observed. Upper limits for a benchmark model on the product of cross section and branching fraction for the production of these heavy narrow resonances are presented. The limit excludes leptophobic Z′ bosons with masses below 2.5TeV within the benchmark model. This is the first result to constrain a leptophobic Z′ resonance in the four-lepton channel.Article Citation - WoS: 13Citation - Scopus: 21Search for Standard Model Production of Four Top Quarks in Proton–proton Collisions at S=13 Tev(Elsevier Ltd., 2017) CMS Collaboration; Karapınar, GülerA search for events containing four top quarks (tt¯tt¯) is reported from proton–proton collisions recorded by the CMS experiment at s=13 TeV and corresponding to an integrated luminosity of 2.6 fb−1. The analysis considers the single-lepton (e or μ)+jets and the opposite-sign dilepton (μ+μ−, μ±e∓, or e+e−)+jets channels. It uses boosted decision trees to combine information on the global event and jet properties to distinguish between tt¯tt¯ and tt¯ production. The number of events observed after all selection requirements is consistent with expectations from background and standard model signal predictions, and an upper limit is set on the cross section for tt¯tt¯ production in the standard model of 94 fb at 95% confidence level (10.2 × the prediction), with an expected limit of 118 fb. This is combined with the results from the published CMS search in the same-sign dilepton channel, resulting in an improved limit of 69 fb at 95% confidence level (7.4 × the prediction), with an expected limit of 71 fb. These are the strongest constraints on the rate of tt¯tt¯ production to date.Article Citation - WoS: 27Citation - Scopus: 32Measurements of the Charm Jet Cross Section and Nuclear Modification Factor in Ppb Collisions at Snn=5.02 Tev(Elsevier Ltd., 2017) CMS Collaboration; Karapınar, GülerThe CMS Collaboration presents the first measurement of the differential cross section of jets from charm quarks produced in proton–lead (pPb) collisions at a nucleon–nucleon center-of-mass energy of sNN=5.02TeV, as well as results from charm quark jets in proton–proton (pp) collisions at s=2.76 and 5.02TeV. By comparing the yields of the pPb and pp collision systems at the same energy, a nuclear modification factor for charm jets from 55 to 400 GeV/c in pPb collisions at sNN=5.02TeV of RpA=0.92±0.07(stat)±0.11(syst) is obtained. This is consistent with an absence of final-state energy loss for charm quarks in pPb collisions. In addition, the fraction of jets coming from charm quarks is found to be consistent with that predicted by PYTHIA 6 for pp collisions at s=2.76 and 5.02TeV, and is independent of the jet transverse momentum from 55 to 400 GeV/c.Article Citation - WoS: 40Citation - Scopus: 131Coherent J/? Photoproduction in Ultra-Peripheral Pbpb Collisions at Snn=2.76tev With the Cms Experiment(Elsevier Ltd., 2017) CMS Collaboration; Karapınar, GülerThe cross section for coherent J/ψ photoproduction accompanied by at least one neutron on one side of the interaction point and no neutron activity on the other side, Xn0n, is measured with the CMS experiment in ultra-peripheral PbPb collisions at sNN=2.76TeV. The analysis is based on a data sample corresponding to an integrated luminosity of 159μb−1, collected during the 2011 PbPb run. The J/ψ mesons are reconstructed in the dimuon decay channel, while neutrons are detected using zero degree calorimeters. The measured cross section is dσXn0n coh/dy(J/ψ)=0.36±0.04(stat)±0.04(syst) mb in the rapidity interval 1.8<|y|<2.3. Using a model for the relative rate of coherent photoproduction processes, this Xn0n measurement gives a total coherent photoproduction cross section of dσcoh/dy(J/ψ)=1.82±0.22(stat)±0.20(syst)±0.19(theo) mb. The data strongly disfavor the impulse approximation model prediction, indicating that nuclear effects are needed to describe coherent J/ψ photoproduction in γ+Pb interactions. The data are found to be consistent with the leading twist approximation, which includes nuclear gluon shadowing.Article Citation - Scopus: 18Search for High-Mass Z Resonances in Proton–proton Collisions at S=8 and 13 Tev Using Jet Substructure Techniques(Elsevier Ltd., 2017) CMS Collaboration; Karapınar, GülerA search for massive resonances decaying to a Z boson and a photon is performed in events with a hadronically decaying Z boson candidate, separately in light-quark and b quark decay modes, identified using jet substructure and advanced b tagging techniques. Results are based on samples of proton–proton collisions collected with the CMS detector at the LHC at center-of-mass energies of 8 and 13TeV, corresponding to integrated luminosities of 19.7 and 2.7 fb−1, respectively. The results of the search are combined with those of a similar search in the leptonic decay modes of the Z boson, based on the same data sets. Spin-0 resonances with various widths and with masses in a range between 0.2 and 3.0TeV are considered. No significant excess is observed either in the individual analyses or the combination. The results are presented in terms of upper limits on the production cross section of such resonances and constitute the most stringent limits to date for a wide range of masses.Article Citation - WoS: 31Citation - Scopus: 33Search for Single Production of a Heavy Vector-Like T Quark Decaying To a Higgs Boson and a Top Quark With a Lepton and Jets in the Final State(Elsevier Ltd., 2017) CMS Collaboration; Karapınar, GülerA search for single production of vector-like top quark partners (T) decaying into a Higgs boson and a top quark is performed using data from pp collisions at a centre-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 2.3 fb−1. The top quark decay includes an electron or a muon while the Higgs boson decays into a pair of b quarks. No significant excess over standard model backgrounds is observed. Exclusion limits on the product of the production cross section and the branching fraction are derived in the T quark mass range 700 to 1800 GeV. For a mass of 1000 GeV, values of the product of the production cross section and the branching fraction greater than 0.8 and 0.7 pb are excluded at 95% confidence level, assuming left- and right-handed coupling of the T quark to standard model particles, respectively. This is the first analysis setting exclusion limits on the cross section of singly produced vector-like T quarks at a centre-of-mass energy of 13 TeV.