Rectorate / Rektörlük
Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
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Correction Citation - WoS: 12Citation - Scopus: 17Search for a New Scalar Resonance Decaying To a Pair of Z Bosons in Proton-Proton Collisions at Root S = 13 Tev (vol 6, 127, 2018)(Springer, 2019) Karapınar, Güler; CMS CollaborationIn both panels of figure 11, the unit of the z axis was mistakenly written as pb when it should have been fb. The corrected versions are shown in figure 1.Article Citation - WoS: 17Citation - Scopus: 22A Search for New Phenomena in Pp Collisions at √s=13tev in Final States With Missing Transverse Momentum and at Least One Jet Using the Αt Variable(Springer, 2017) CMS Collaboration; Karapınar, GülerA search for new phenomena is performed in final states containing one or more jets and an imbalance in transverse momentum in pp collisions at a centre-of-mass energy of 13TeV. The analysed data sample, recorded with the CMS detector at the CERN LHC, corresponds to an integrated luminosity of 2.3fb-1. Several kinematic variables are employed to suppress the dominant background, multijet production, as well as to discriminate between other standard model and new physics processes. The search provides sensitivity to a broad range of new-physics models that yield a stable weakly interacting massive particle. The number of observed candidate events is found to agree with the expected contributions from standard model processes, and the result is interpreted in the mass parameter space of fourteen simplified supersymmetric models that assume the pair production of gluinos or squarks and a range of decay modes. For models that assume gluino pair production, masses up to 1575 and 975GeV are excluded for gluinos and neutralinos, respectively. For models involving the pair production of top squarks and compressed mass spectra, top squark masses up to 400GeV are excluded. © 2017, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 15Citation - Scopus: 20Measurements of the Pp -> W Gamma Gamma and Pp -> Z Gamma Gamma Cross Sections and Limits on Anomalous Quartic Gauge Couplings at Root S=8 Tev(Springer, 2017) Karapınar, Güler; CMS CollaborationMeasurements are presented of W gamma gamma and Z gamma gamma production in proton-proton collisions. Fiducial cross sections are reported based on a data sample corresponding to an integrated luminosity of 19.4 fb(-1) collected with the CMS detector at a center-of-mass energy of 8 TeV. Signal is identified through the W -> lv and Z -> ll decay modes, where l is a muon or an electron. The production of W gamma gamma and Z gamma gamma, measured with significances of 2.6 and 5.9 standard deviations, respectively, is consistent with standard model predictions. In addition, limits on anomalous quartic gauge couplings in W gamma gamma production are determined in the context of a dimension-8 effective field theory.Article Citation - WoS: 46Citation - Scopus: 52Search for a Charged Higgs Boson Decaying To Charm and Bottom Quarks in Proton-Proton Collisions at Root S=8tev(Springer, 2018) Karapınar, Güler; CMS CollaborationA search for charged Higgs boson decaying to a charm and a bottom quark pair production in which one top quark decays to a charged Higgs boson and a bottom quark and the other decays to a charged lepton, a neutrino, and a bottom quark. Charged Higgs boson decays to are searched for, resulting in a final state containing at least four jets, a charged lepton (muon or electron), and missing transverse momentum. A kinematic fit is performed to identify the pair of jets least likely to be the bottom quarks originating from direct top quark decays and the invariant mass of this pair is used as the final observable in the search. No evidence for the presence of a charged Higgs boson is observed and upper limits at 95% confidence level of 0.8-0.5% are set on the branching fraction B(t H(+)b), assuming B(H+ = 1.0 and B(t H(+)b) + B(t Wb) = 1.0, for the charged Higgs boson mass range 90-150 GeV.Article Citation - WoS: 54Citation - Scopus: 76Search for Heavy Majorana Neutrinos in Same-Sign Dilepton Channels in Proton-Proton Collisions at Root S = Tev(Springer, 2019) Karapınar, Güler; CMS CollaborationA search is performed for a heavy Majorana neutrino (N), produced in leptonic decay of a W boson propagator and decaying into a W boson and a lepton, with the CMS detector at the LHC. The signature used in this search consists of two same-sign leptons, in any flavor combination of electrons and muons, and at least one jet. The data were collected during 2016 in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). The results are found to be consistent with the expected standard model background. Upper limits are set in the mass range between 20 and 1600 GeV in the context of a Type-I seesaw mechanism, on |V-eN|(2), |V-N|(2), and |VeNV *|(2)/(|V-eN|(2)+|V-N|(2)), where V-N is the matrix element describing the mixing of N with the standard model neutrino of flavor = e, . For N masses between 20 and 1600 GeV, the upper limits on |V-N|(2) range between 2.3 x 10(-5) and unity. These are the most restrictive direct limits for heavy Majorana neutrino masses above 430 GeV.Article Citation - WoS: 12Citation - Scopus: 19Inclusive Search for Supersymmetry in Pp Collisions at Root S=13 Tev Using Razor Variables and Boosted Object Identification in Zero and One Lepton Final States(Springer, 2019) Karapınar, Güler; CMS CollaborationAn inclusive search for supersymmetry (SUSY) using the razor variables is performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of 35.9 fb(-1), collected with the CMS experiment in 2016 at a center-of-mass energy of =13 TeV. The search looks for an excess of events with large transverse energy, large jet multiplicity, and large missing transverse momentum. The razor kinematic variables are sensitive to large mass differences between the parent particle and the invisible particles of a decay chain and help to identify the presence of SUSY particles. The search covers final states with zero or one charged lepton and features event categories divided according to the presence of a high transverse momentum hadronically decaying W boson or top quark, the number of jets, the number of b-tagged jets, and the values of the razor kinematic variables, in order to separate signal from background for a broad range of SUSY signatures. The addition of the boosted W boson and top quark categories within the analysis further increases the sensitivity of the search, particularly to signal models with large mass splitting between the produced gluino or squark and the lightest SUSY particle. The analysis is interpreted using simplified models of R-parity conserving SUSY, focusing on gluino pair production and top squark pair production. Limits on the gluino mass extend to 2.0 TeV, while limits on top squark mass reach 1.14 TeV.Article Citation - WoS: 137Citation - Scopus: 174Search for Narrow and Broad Dijet Resonances in Proton-Proton Collisions at ?s=13 Tev and Constraints on Dark Matter Mediators and Other New Particles(Springer, 2018) CMS Collaboration; Karapınar, GülerSearches for resonances decaying into pairs of jets are performed using proton-proton collision data collected at s=13 TeV corresponding to an integrated luminosity of up to 36 fb−1. A low-mass search, for resonances with masses between 0.6 and 1.6 TeV, is performed based on events with dijets reconstructed at the trigger level from calorimeter information. A high-mass search, for resonances with masses above 1.6 TeV, is performed using dijets reconstructed offline with a particle-flow algorithm. The dijet mass spectrum is well described by a smooth parameterization and no evidence for the production of new particles is observed. Upper limits at 95% confidence level are reported on the production cross section for narrow resonances with masses above 0.6 TeV. In the context of specific models, the limits exclude string resonances with masses below 7.7 TeV, scalar diquarks below 7.2 TeV, axigluons and colorons below 6.1 TeV, excited quarks below 6.0 TeV, color-octet scalars below 3.4 TeV, W′ bosons below 3.3 TeV, Z′ bosons below 2.7 TeV, Randall-Sundrum gravitons below 1.8 TeV and in the range 1.9 to 2.5 TeV, and dark matter mediators below 2.6 TeV. The limits on both vector and axial-vector mediators, in a simplified model of interactions between quarks and dark matter particles, are presented as functions of dark matter particle mass and coupling to quarks. Searches are also presented for broad resonances, including for the first time spin-1 resonances with intrinsic widths as large as 30% of the resonance mass. The broad resonance search improves and extends the exclusions of a dark matter mediator to larger values of its mass and coupling to quarks.Article Citation - WoS: 98Citation - Scopus: 89Measurement of the Cross Section for Top Quark Pair Production in Association With a W or Z Boson in Proton-Proton Collisions at ?s = 13 Tev(Springer, 2018) Karapınar, GülerA measurement is performed of the cross section of top quark pair production in association with a W or Z boson using proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb−1, collected by the CMS experiment in 2016. The measurement is performed in the same-sign dilepton, three- and four-lepton final states. The production cross sections are measured to be σ(tt¯W)=0.77−0.11+0.12(stat)−0.12+0.13(syst)pb and σ(tt¯Z)=0.99−0.08+0.09(stat)−0.10+0.12(syst)pb. The expected (observed) signal significance for the t t ¯ W production in same-sign dilepton channel is found to be 4.5 (5.3) standard deviations, while for the t t ¯ Z production in three- and four-lepton channels both the expected and the observed significances are found to be in excess of 5 standard deviations. The results are in agreement with the standard model predictions and are used to constrain the Wilson coefficients for eight dimension-six operators describing new interactions that would modify t t ¯ W and t t ¯ Z production.Article Citation - WoS: 61Citation - Scopus: 67Search for Top Squark Pair Production in Pp Collisions at ?s=13 Tev Using Single Lepton Events(Springer, 2017) CMS Collaboration; Karapınar, GülerA search for top squark pair production in pp collisions at s=13 TeV is performed using events with a single isolated electron or muon, jets, and a large transverse momentum imbalance. The results are based on data collected in 2016 with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb−1. No significant excess of events is observed above the expectation from standard model processes. Exclusion limits are set in the context of supersymmetric models of pair production of top squarks that decay either to a top quark and a neutralino or to a bottom quark and a chargino. Depending on the details of the model, we exclude top squarks with masses as high as 1120 GeV. Detailed information is also provided to facilitate theoretical interpretations in other scenarios of physics beyond the standard model.Article Citation - WoS: 12Citation - Scopus: 36Measurement of the Semileptonic T T ¯ + ? Production Cross Section in Pp Collisions at ?s=8 Tev(Springer, 2017) CMS Collaboration; Karapınar, GülerA measurement of the cross section for top quark-antiquark (t t ¯) pairs produced in association with a photon in proton-proton collisions at s=8 TeV is presented. The analysis uses data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.7 fb1. The signal is defined as the production of a t t ¯ pair in association with a photon having a transverse energy larger than 25 GeV and an absolute pseudorapidity smaller than 1.44. The measurement is performed in the fiducial phase space corresponding to the semileptonic decay chain of the t t ¯ pair, and the cross section is measured relative to the inclusive t t ¯ pair production cross section. The fiducial cross section for associated t t ¯ pair and photon production is found to be 127 ±27 (stat+syst) fb per semileptonic final state. The measured value is in agreement with the theoretical prediction.