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: 456Citation - Scopus: 423Description and Performance of Track and Primary-Vertex Reconstruction With the Cms Tracker(IOP Publishing Ltd., 2014) Demir, Durmuş Ali; CMS CollaborationA description is provided of the software algorithms developed for the CMS tracker both for reconstructing charged-particle trajectories in proton-proton interactions and for using the resulting tracks to estimate the positions of the LHC luminous region and individual primary-interaction vertices. Despite the very hostile environment at the LHC, the performance obtained with these algorithms is found to be excellent. For t (t) over bar events under typical 2011 pileup conditions, the average track-reconstruction efficiency for promptly-produced charged particles with transverse momenta of p(T) > 0.9GeV is 94% for pseudorapidities of vertical bar eta vertical bar < 0.9 and 85% for 0.9 < vertical bar eta vertical bar < 2.5. The inefficiency is caused mainly by hadrons that undergo nuclear interactions in the tracker material. For isolated muons, the corresponding efficiencies are essentially 100%. For isolated muons of p(T) = 100GeV emitted at vertical bar eta vertical bar < 1.4, the resolutions are approximately 2.8% in p(T), and respectively, 10 m m and 30 mu m in the transverse and longitudinal impact parameters. The position resolution achieved for reconstructed primary vertices that correspond to interesting pp collisions is 10-12 mu m in each of the three spatial dimensions. The tracking and vertexing software is fast and flexible, and easily adaptable to other functions, such as fast tracking for the trigger, or dedicated tracking for electrons that takes into account bremsstrahlung.Article Citation - WoS: 77Citation - Scopus: 86Measurement of the Isolated Prompt Photons Production Cross Section in Pp Collisions at ?s=7tev(American Physical Society, 2011) Karapınar, Güler; Demir, Durmuş AliThe differential cross section for the inclusive production of isolated prompt photons has been measured as a function of the photon transverse energy ETγ in pp collisions at √s=7TeV using data recorded by the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.9pb-1. Photons are required to have a pseudorapidity |ηγ|<1.45 and ETγ>21GeV, covering the kinematic region 0.006<xT<0.086. The measured cross section is found to be in agreement with next-to-leading-order perturbative QCD calculations. © 2011 American Physical Society.Article Citation - WoS: 610Citation - Scopus: 672Observation and Studies of Jet Quenching in Pbpb Collisions at ?snn=2.76 Tev(American Physical Society, 2011) Karapınar, Güler; Demir, Durmuş AliJet production in PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV was studied with the Compact Muon Solenoid (CMS) detector at the LHC, using a data sample corresponding to an integrated luminosity of 6.7μb-1. Jets are reconstructed using the energy deposited in the CMS calorimeters and studied as a function of collision centrality. With increasing collision centrality, a striking imbalance in dijet transverse momentum is observed, consistent with jet quenching. The observed effect extends from the lower cutoff used in this study (jet pT=120 GeV/c) up to the statistical limit of the available data sample (jet pT≈210 GeV/c). Correlations of charged particle tracks with jets indicate that the momentum imbalance is accompanied by a softening of the fragmentation pattern of the second most energetic, away-side jet. The dijet momentum balance is recovered when integrating low transverse momentum particles distributed over a wide angular range relative to the direction of the away-side jet. © 2011 American Physical Society.Article Citation - WoS: 71Citation - Scopus: 88Measurement of the Differential Cross Section for Isolated Prompt Photon Production in Pp Collisions at 7 Tev(American Physical Society, 2011) Karapınar, Güler; Demir, Durmuş AliA measurement of the differential cross section for the inclusive production of isolated prompt photons in proton-proton collisions at a center-of-mass energy of 7 TeV is presented. The data sample corresponds to an integrated luminosity of 36pb-1 recorded by the CMS detector at the LHC. The measurement covers the pseudorapidity range |η|<2.5 and the transverse energy range 25<ET<400GeV, corresponding to the kinematic region 0.007<xT<0.114. Photon candidates are identified with two complementary methods, one based on photon conversions in the silicon tracker and the other on isolated energy deposits in the electromagnetic calorimeter. The measured cross section is presented as a function of ET in four pseudorapidity regions. The next-to-leading-order perturbative QCD calculations are consistent with the measured cross section. © 2011 CERN.Article Citation - WoS: 51Citation - Scopus: 58Search for New Physics With a Monojet and Missing Transverse Energy in Pp Collisions at ?s=7tev(American Physical Society, 2011) Karapınar, Güler; Demir, Durmuş AliA study of events with missing transverse energy and an energetic jet is performed using pp collision data at a center-of-mass energy of 7 TeV. The data were collected by the CMS detector at the LHC, and correspond to an integrated luminosity of 36pb-1. An excess of these events over standard model contributions is a signature of new physics such as large extra dimensions and unparticles. The number of observed events is in good agreement with the prediction of the standard model, and significant extension of the current limits on parameters of new physics benchmark models is achieved. © 2011 CERN.Article Citation - WoS: 136Citation - Scopus: 115Measurement of the Underlying Event Activity at the Lhc With ?s = 7 Tev and Comparison With ?s = 0:9 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliA measurement of the underlying activity in events with a jet of transverse momentum in the several GeV region is performed in proton-proton collisions at √ s = 0:9 and 7TeV, using data collected by the CMS experiment at the LHC. The production of charged particles with pseudorapidity |η|<2 and transverse momentum pT >0:5 GeV/c is studied in the azimuthal region transverse to that of the leading set of charged particles forming a track-jet. A significant growth of the average multiplicity and scalar-pT sum of the particles in the transverse region is observed with increasing pT of the leading trackjet, followed by a much slower rise above a few GeV/c. For track-jet pT larger than a few GeV/c, the activity in the transverse region is approximately doubled with a centreof- mass energy increase from 0:9 to 7TeV. Predictions of several QCD-inspired models as implemented in pythia are compared to the data.Article Citation - WoS: 55Citation - Scopus: 70Search for a Vectorlike Quark With Charge 2/3 in T+z Events From Pp Collisions at ?s=7tev(American Physical Society, 2011) Karapınar, Güler; Demir, Durmuş AliA search for pair-produced heavy vectorlike charge-2/3 quarks, T, in pp collisions at a center-of-mass energy of 7 TeV, is performed with the CMS detector at the LHC. Events consistent with the flavor-changing-neutral-current decay of a T quark to a top quark and a Z boson are selected by requiring two leptons from the Z-boson decay, as well as an additional isolated charged lepton. In a data sample corresponding to an integrated luminosity of 1.14fb -1, the number of observed events is found to be consistent with the standard model background prediction. Assuming a branching fraction of 100% for the decay T→tZ, a T quark with a mass less than 475GeV/c 2 is excluded at the 95% confidence level. © 2011 CERN.