Rectorate / Rektörlük
Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
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Article Citation - WoS: 14Citation - Scopus: 32Search for Physics Beyond the Standard Model in Opposite-Sign Dilepton Events in Pp Collisions at Root S=7 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliA search is presented for physics beyond the standard model (SM) in final states with opposite-sign isolated lepton pairs accompanied by hadronic jets and missing transverse energy. The search is performed using LHC data recorded with the CMS detector, corresponding to an integrated luminosity of 34 pb(-1). No evidence for an event yield beyond SM expectations is found. An upper limit on the non-SM contribution to the signal region is deduced from the results. This limit is interpreted in the context of the constrained minimal supersymmetric model. Additional information is provided to allow testing the exclusion of specific models of physics beyond the SM.Article Citation - WoS: 14Citation - Scopus: 50Search for Supersymmetry in Events With a Lepton, a Photon, and Large Missing Transverse Energy in Pp Collisions at Root S=7 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliA search is performed for an excess of events, over the standard model expectations, with a photon, a lepton, and large missing transverse energy in pp collisions root s = 7TeV. Such events are expected in many new physics models, in particular a theory that is broken via a gauge-mediated mechanism, when the lightest and neutral gauginos are mass degenerate. The data sample used in this search to an integrated luminosity of 35 pb(-1) collected with the CMS detector at the No evidence of such an excess above the standard model backgrounds, dominated by production, is found. The results are presented as 95% confidence level upper limits on the cross section for a benchmark gauge-mediated scenario, and are then converted into exclusion limits on the squark, gluino, and wino masses.Article Citation - WoS: 28Search for a Heavy Bottom-Like Quark in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2011) Demir, Durmuş Ali; Karapınar, GülerA search for pair-produced bottom-like quarks in pp collisions at root s = 7 TeV is conducted with the CMS experiment at the LHC. The decay b' -> tW is considered in this search. The b'(b) over bar' tW-(t) over barW(+) process can be identified by the distinctive signature of trileptons and same-sign dileptons. With a data sample corresponding to an integrated luminosity of 34 pb(-1), no excess above the standard model background predictions is observed and a b' quark with a mass between 255 and 361 GeV/c(2) is excluded at the 95% confidence level. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 39Citation - Scopus: 45Search for Same-Sign Top-Quark Pair Production at Root S=7 Tev and Limits on Flavour Changing Neutral Currents in the Top Sector(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliAn inclusive search for same-sign top-quark pair production in pp collisions at root s = 7 TeV is performed using a data sample recorded with the CMS detector in 2010, corresponding to an integrated luminosity of 35 pb(-1). This analysis is motivated by recent studies of p (p) over bar -> t (t) over bar reporting mass-dependent forward-backward asymmetries larger than expected from the standard model. These asymmetries could be due to Flavor Changing Neutral Currents (FCNC) in the top sector induced by t -channel exchange of a massive neutral vector boson (Z'). Models with such a Z' also predict enhancement of same-sign top-pair production in pp or pp collisions. Limits are set as a function of the Z' mass and its couplings to u and t quarks. These limits disfavour the FCNC interpretation of the Tevatron results.Article Citation - WoS: 102Citation - Scopus: 120Dependence on Pseudorapidity and on Centrality of Charged Hadron Production in Pbpb Collisions at Root S(nn)=2.76 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliA measurement is presented of the charged hadron multiplicity in hadronic PbPb collisions, as a function of pseudorapidity and centrality, at a collision energy of 2.76 TeV per nucleon pair. The data sample is collected using the CMS detector and a minimum-bias trigger, with the CMS solenoid off. The number of charged hadrons is measured both by counting the number of reconstructed particle hits and by forming hit doublets of pairs of layers in the pixel detector. The two methods give consistent results. The charged hadron multiplicity density, dN(ch)/d eta vertical bar(eta=0), for head-on collisions is found to be 1612 +/- 55, where the uncertainty is dominated by systematic effects. Comparisons of these results to previous measurements and to various models are also presented.Article Citation - WoS: 21Measurement of the Ratio of the 3-Jet To 2-Jet Cross Sections in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2011) Demir, Durmuş Ali; Karapınar, GülerA measurement of the ratio of the inclusive 3-jet to 2-jet cross sections as a function of the total jet transverse momentum. HT, in the range 0.2 < H-T < 2.5 TeV is presented. The data have been collected at a proton-proton centre-of-mass energy of 7 TeV with the CMS detector at the LHC, and correspond to an integrated luminosity of 36 pb(-1). Comparisons are made between the data and the predictions of different QCD-based Monte Carlo models for multijet production. All models considered in this study are consistent with the data for H-T > 0.5 TeV. This measurement extends to an H-T range that has not been explored before. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 33Search for Physics Beyond the Standard Model Using Multilepton Signatures in Pp Collisions at Root S=7 Tev(Elsevier Ltd., 2011) Demir, Durmuş Ali; Karapınar, GülerA search for physics beyond the standard model in events with at least three leptons and any number of jets is presented. The data sample corresponds to 35 pb(-1) of integrated luminosity in pp collisions at root s = 7 TeV collected by the CMS experiment at the LHC. A number of exclusive multileptonic channels are investigated and standard model backgrounds are suppressed by requiring sufficient missing transverse energy, invariant mass inconsistent with that of the Z boson, or high jet activity. Control samples in data are used to ascertain the robustness of background evaluation techniques and to minimise the reliance on simulation. The observations are consistent with background expectations. These results constrain previously unexplored regions of supersymmetric parameter space. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 81Search for Supersymmetry in Hadronic Final States Using M-T2 in Pp Collisions at Root S=7 Tev(Springer Verlag, 2012) Karapınar, Güler; Demir, Durmuş AliA search for supersymmetry or other new physics resulting in similar final states is presented using a data sample of 4.73 fb(-1) of pp collisions collected at root s = 7 TeV with the CMS detector at the LHC. Fully hadronic final states are selected based on the variable M-T2, an extension of the transverse mass in events with two invisible particles. Two complementary studies are performed. The first targets the region of parameter space with medium to high squark and gluino masses, in which the signal can be separated from the standard model backgrounds by a tight requirement on M-T2. The second is optimized to be sensitive to events with a light gluino and heavy squarks. In this case, the M-T2 requirement is relaxed, but a higher jet multiplicity and at least one b-tagged jet are required. No significant excess of events over the standard model expectations is observed. Exclusion limits are derived for the parameter space of the constrained minimal supersymmetric extension of the standard model, as well as on a variety of simplified model spectra.Article Citation - WoS: 52Citation - Scopus: 61Measurement of the Zz Production Cross Section and Search for Anomalous Couplings in 2l2l' Final States in Pp Collisions at Root S=7 Tev(Springer Verlag, 2013) Karapınar, Güler; Demir, Durmuş AliA measurement is presented of the ZZ production cross section in the ZZ -> 2l2l' decay mode with l = e, mu and l' = e, mu, tau in proton-proton collisions at root s = 7 TeV with the CMS experiment at the LHC. Results are based on data corresponding to an integrated luminosity of 5.0 fb(-1). The measured cross section sigma(pp -> ZZ) = 6.24(-080)(+0.86) (stat.)(-0.32)(+0.41) (syst.) +/- 0.14 (lumi.) pb is consistent with the standard model predictions. The following limits on ZZZ and ZZ-gamma anomalous trilinear gauge couplings are set at 95% confidence level: -0.011 < f(4)(Z) < 0.012, -0.012 < f(5)(Z) < 0.012, -0.013 < f(4)(gamma) < 0.015, and -0.014 < f(5)(gamma) < 0.014.Article Citation - WoS: 58Citation - Scopus: 58Search for Narrow Resonances and Quantum Black Holes in Inclusive and B-Tagged Dijet Mass Spectra From Pp Collisions at Root S=7 Tev(Springer Verlag, 2013) Karapınar, Güler; Demir, Durmuş AliA search for narrow resonances and quantum black holes is performed in inclusive and b-tagged dijet mass spectra measured with the CMS detector at the LHC. The data set corresponds to 5 fb(-1) of integrated luminosity collected in pp collisions at root s = 7 TeV. No narrow resonances or quantum black holes are observed. Model-independent upper limits at the 95% confidence level are obtained on the product of the cross section, branching fraction into dijets, and acceptance for three scenarios: decay into quark-quark, quark-gluon, and gluon-gluon pairs. Specific lower limits are set on the mass of string resonances (4.31 TeV), excited quarks (3.32 TeV), axigluons and colorons (3.36 TeV), scalar color-octet resonances (2.07 TeV), E-6 diquarks (3.75 TeV), and on the masses of W' (1.92 TeV) and Z' (1.47 TeV) bosons. The limits on the minimum mass of quantum black holes range from 4 to 5.3 TeV. In addition, b-quark tagging is applied to the two leading jets and upper limits are set on the production of narrow dijet resonances in a model-independent fashion as a function of the branching fraction to b-jet pairs.