Rectorate / Rektörlük
Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
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Article Citation - WoS: 26Citation - Scopus: 54Search for Heavy Stable Charged Particles in Pp Collisions at Root S=7 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliThe result of a search at the LHC for heavy stable charged particles produced in pp collisions at root s = 7TeV is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb(-1). Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398 GeV/c(2), using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon detectors. A lower limit of 311 GeV/c(2) is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this particle becomes neutral before reaching the muon detectors.Article Citation - WoS: 153Citation - Scopus: 137Strange Particle Production in Pp Collisions at Root S=0.9 and 7 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliThe spectra of strange hadrons are measured in proton-proton collisions, recorded by the CMS experiment at the CERN LHC, at centre-of-mass energies of 0.9 and 7TeV. The K-S(0), A, and Xi(-) particles and their antiparticles are reconstructed from their decay topologies and the production rates are measured as functions of rapidity and transverse momentum, p(T). The results are compared to other experiments and to predictions of the PYTHIA Monte Carlo program. The p(T) distributions are found to differ substantially from the PYTHIA results and the production rates exceed the predictions by up to a factor of three.Article Citation - WoS: 18Citation - Scopus: 29Search for Large Extra Dimensions in the Diphoton Final State at the Large Hadron Collider(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliA search for large extra spatial dimensions via virtual-graviton exchange in the diphoton channel has been carried out with the CMS detector at the LHC. No excess of events above the standard model expectations is found using a data sample collected in proton-proton collisions at root s = 7TeV and corresponding to an integrated luminosity of 36 pb(-1). New lower limits on the effective Planck scale in the range of 1.6-2.3TeV at the 95% confidence level are set, providing the most restrictive bounds to date on models with more than two large extra dimensions.Article Citation - WoS: 30Citation - Scopus: 37Search for Supersymmetry in Events With B Jets and Missing Transverse Momentum at the Lhc(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliA search for supersymmetry is presented using a sample of events with b jets and missing transverse momentum. The search uses a data sample of proton-proton collisions at a centre-of-mass energy of 7TeV, corresponding to an integrated luminosity of 35 pb(-1), collected with the CMS detector. A total of 0.33(-0.33)(+0.43) (stat.) +/- 0.13 (syst.) events is predicted, using control samples in the data, to arise from standard model processes, and one event is observed in the data. Upper limits are set at the 95% confidence level on the cross sections of benchmark supersymmetric models.Article Citation - WoS: 25Citation - Scopus: 87Measurement of the T(t)over-Bar Production Cross Section and the Top Quark Mass in the Dilepton Channel in Pp Collisions at Root S=7 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliThe t (t) over bar production cross section and top quark mass are measured in proton-proton collisions at root s = 7 TeV in a data sample corresponding to an integrated luminosity of 36 pb(-1) collected by the CMS experiment. The measurements are performed in events with two leptons (electrons or muons) in the final state. Results of the cross section measurement in events with and without b-quark identification are obtained and combined. The measured value is sigma(tt) - 168 +/- 18 (stat:) +/- 14 (syst:) +/- 7 (lumi:) pb, consistent with predictions from the standard model. The top quark mass m(top) is reconstructed with two different methods, a full kinematic analysis and a matrix weighting technique. The combination yields a measurement of m(top) = 175.5 +/- 4.6 (stat:) +/- 4: 6 (syst:) GeV/c(2).Article Citation - WoS: 103Long-Range and Short-Range Dihadron Angular Correlations in Central Pbpb Collisions at Root S(nn)=2.76 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliFirst measurements of dihadron correlations for charged particles are presented for central PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV over a broad range in relative pseudorapidity (Delta eta) and the full range of relative azimuthal angle (Delta phi). The data were collected with the CMS detector, at the LHC. A broadening of the away-side (Delta phi approximate to pi) azimuthal correlation is observed at all Delta eta, as compared to the measurements in pp collisions. Furthermore, long-range dihadron correlations in Delta eta are observed for particles with similar phi values. This phenomenon, also known as the "ridge", persists up to at least vertical bar Delta eta vertical bar = 4. For particles with transverse momenta (p(T)) of 2-4 GeV/c, the ridge is found to be most prominent when these particles are correlated with particles of p(T) = 2-6 GeV/c, and to be much reduced when paired with particles of p(T) = 10-12 GeV/c.Article Citation - WoS: 42Citation - Scopus: 38Measurement of the Inclusive Z Cross Section Via Decays To Tau Pairs in Pp Collisions at Root S=7 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliThe first measurement of inclusive Z > tau(+) tau(-) production in pp collisions at the LHC is presented, in the final states mu+hadrons, e+hadrons, e-mu, and mu+mu. The data sample corresponds to an integrated luminosity of 36 pb(-1) collected with the CMS detector. The measured cross section is sigma (pp -> ZX) x B (Z -> tau(+)tau(-)) = 1.00 +/- 0.05 (stat.)+/- 0.08 (syst.) +/- 0.04 (lumi.) nb, which is in good agreement with the next-to-next-to-leading order QCD prediction and improves on previous measurements in the Z -> e(+)e(-) and mu(+)mu(-) channels. The reconstruction efficiency for hadronic T decays is determined with a precision of 7%.Article Citation - WoS: 2Search for the Standard Model Higgs Boson Produced in Association With W and Z Bosons in Pp Collisions at Root S=7 Tev(Springer Verlag, 2012) Karapınar, Güler; Demir, Durmuş AliA search for the Higgs boson produced in association with a W or Z boson in proton-proton collisions at a center-of-mass energy of 7 TeV is performed with the CMS detector at the LHC using the full 2011 data sample, from an integrated luminosity of 5 fb(-1). Higgs boson decay modes to tau tau and WW are explored by selecting events with three or four leptons in the final state. No excess above background expectations is observed, resulting in exclusion limits on the product of Higgs associated production cross section and decay branching fraction for Higgs boson masses between 110 and 200 GeV in these channels. Combining these results with other CMS associated production searches using the same dataset in the H -> gamma gamma and H -> b (b) over bar decay modes, the cross section for associated Higgs boson production 3.3 times the standard model expectation or larger is ruled out at the 95% confidence level for a Higgs boson mass of 125 GeV.Article Citation - WoS: 11Measurement of the Production Cross Section for Z Gamma -> Nu(nu)over-Bar Gamma in Pp Collisions at Root S=7 Tev and Limits on Zz Gamma and Z Gamma Gamma Triple Gauge Boson Couplings(Springer Verlag, 2013) Karapınar, Güler; Demir, Durmuş AliA measurement of the Z gamma -> nu(nu) over bar gamma cross section in pp collisions at root s = 7 TeV is presented, using data corresponding to an integrated luminosity of 5.0 fb(-1) collected with the CMS detector. This measurement is based on the observation of events with an imbalance of transverse energy in excess of 130 GeV and a single photon in the absolute pseudorapidity range vertical bar eta vertical bar < 1.4 with transverse energy above 145 GeV. The Z gamma -> nu<(nu)over bar>gamma production cross section is measured to be 21.1 +/- 4.2(stat.)+/- 4.3(syst.)+/- 0.5(lum.)fb, which agrees with the standard model prediction of 21.9 +/- 1.1 fb. The results are combined with the CMS measurement of Z gamma production in the l(+)l(-)gamma final state (where l is an electron or a muon) to yield the most stringent limits to date on triple gauge boson couplings. vertical bar h(3)(Z)vertical bar < 2.7 x 10(-3), vertical bar h(4)(Z)vertical bar < 1.3 x 10(-5) for ZZ gamma and vertical bar h(3)(gamma)vertical bar < 2.9 x 10(-3), vertical bar h(4)(gamma)vertical bar < 1.5 x 10(-5) for Z gamma gamma couplings.Article Citation - WoS: 31Citation - Scopus: 58Measurement of the Tt̄ production cross section in the dilepton channel in Pp collisions at √s = 8 Tev(Springer Verlag, 2014) CMS Collaboration; Demir, Durmuş AliThe top-antitop quark (tt̄) production cross section is measured in proton-proton collisions at √s = 8 TeV with the CMS experiment at the LHC, using a data sample corresponding to an integrated luminosity of 5.3 fb -1. The measurement is performed by analysing events with a pair of electrons or muons, or one electron and one muon, and at least two jets, one of which is identified as originating from hadronisation of a bottom quark. The measured cross section is 239 ± 2 (stat.) ± 11 (syst.) ± 6 (lum.) pb, for an assumed top-quark mass of 172.5 GeV, in agreement with the prediction of the standard model.