Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Article Citation - WoS: 175Citation - Scopus: 144Charged Particle Multiplicities in Pp Interactions at ?s = 0.9, 2.36, and 7tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliMeasurements of primary charged hadron multiplicity distributions are presented for non-single-diffractive events in proton-proton collisions at centre-of-mass energies of √s = 0.9, 2.36, and 7TeV, in five pseudorapidity ranges from |η| < 0.5 to |η| < 2.4. The data were collected with the minimum-bias trigger of the CMS experiment during the LHC commissioning runs in 2009 and the 7TeV run in 2010. The multiplicity distribution at √s = 0.9 TeV is in agreement with previous measurements. At higher energies the increase of the mean multiplicity with √s is underestimated by most event generators. The average transverse momentum as a function of the multiplicity is also presented. The measurement of higher-order moments of the multiplicity distribution confirms the violation of Koba-Nielsen-Olesen scaling that has been observed at lower energies.Article Citation - WoS: 17Citation - Scopus: 32Inclusive B-Hadron Production Cross Section With Muons in Pp Collisions at ?s = 7 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliA measurement of the b-hadron production cross section in proton-proton collisions at √s = 7TeV is presented. The dataset, corresponding to 85 nb-1, was recorded with the CMS experiment at the LHC using a low-threshold single-muon trigger. Events are selected by the presence of a muon with transverse momentum pμ T > 6GeV with respect to the beam direction and pseudorapidity |ζμ| < 2.1. The transverse momentum of the muon with respect to the closest jet discriminates events containing b hadrons from background. The inclusive b-hadron production cross section is presented as a function of muon transverse momentum and pseudorapidity. The measured total cross section in the kinematic acceptance is σ(pp → b + X → μ + X′) = 1.32 ± 0.01(stat) ± 0.30(syst) ± 0.15(lumi)μb.Article Citation - WoS: 242Citation - Scopus: 228Measurements of Inclusive W and Z Cross Sections in Pp Collisions at ?s = 7 Tev the Cms Collaboration(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliMeasurements of inclusive W and Z boson production cross sections in pp collisions at √s = 7 TeV are presented, based on 2.9 pb-1 of data recorded by the CMS detector at the LHC. The measurements, performed in the electron and muon decay channels, are combined to give σ(pp → WX) × B(W → l?) = 9.95 ± 0.07 (stat.) ± 0.28 (syst.) ± 1.09 (lumi.) nb and σ(pp → ZX) × B(Z → l +l-) = 0.931 ± 0.026 (stat.) ± 0.023 (syst.) ± 0.102 (lumi.) nb, where l stands for either e or μ. Theoretical predictions, calculated at the next-to-next-to-leading order in QCD using recent parton distribution functions, are in agreement with the measured cross sections. Ratios of cross sections, which incur an experimental systematic uncertainty of less than 4%, are also reported.Article Citation - WoS: 52Citation - Scopus: 47Measurement of the Drell-Yan Cross Section in Pp Collisions at ? S = 7 Tev(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliThe Drell-Yan differential cross section is measured in pp collisions at √ s = 7TeV, from a data sample collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 36 pb-1. The cross section measurement, normalized to the measured cross section in the Z region, is reported for both the dimuon and dielectron channels in the dilepton invariant mass range 15{600 GeV. The normalized cross section values are quoted both in the full phase space and within the detector acceptance. The effect of final state radiation is also identified. The results are found to agree with theoretical predictions. Copyright CERN.Article Citation - WoS: 255Citation - Scopus: 228Measurement of the Inclusive W and Z Production Cross Sections in Pp Collisions at ?s = 7 Tev With the Cms Experiment(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliA measurement of inclusive W and Z production cross sections in pp collisions at √s = 7TeV is presented. The electron and muon decay channels are analyzed in a data sample collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36 pb-1. The measured inclusive cross sections are σ(pp → WX) × ß(W → lν) = 10.31 × 0.02 (stat.) × 0.09 (syst.) × 0.10 (th.) × 0.41 (lumi.) nb and σ(pp → ZX) x B(Z → l +l- = 0.974 × 0.007 (stat.) × 0.007 (syst.) × 0.018 (th.) × 0.039 (lumi.) nb, limited to the dilepton invariant mass range 60 to 120 GeV. The luminosity-independent cross section ratios are (σ(pp → WX) × B(W → lv))/(σ(pp → ZX) × B(Z → l+l-)) = 10.54 × 0.07 (stat.) × 0.08 (syst.) × 0.16 (th.) and (σ(pp → W+X) × B(W+ → l+ν))/(σ(pp → W-X) × B(W- → l-v̄)) = 1.421×0.006 (stat.) ×0.014 (syst.) ×0.029 (th.). The measured values agree with next-to-next-to-leading order QCD cross section calculations based on recent parton distribution functions. Copyright CERN.Article Citation - WoS: 26Citation - Scopus: 29Search for Light Resonances Decaying Into Pairs of Muons as a Signal of New Physics(Springer Verlag, 2011) Karapınar, Güler; Demir, Durmuş AliA search for groups of collimated muons is performed using a data sample collected by the CMS experiment at the LHC, at a centre-of-mass energy of 7 TeV, and corresponding to an integrated luminosity of 35 pb-1. The analysis searches for production of new low-mass states decaying into pairs of muons and is designed to achieve high sensitivity to a broad range of models predicting leptonic jet signatures. With no excess observed over the background expectation, upper limits on the production cross section times branching fraction times acceptance are set, ranging from 0.1 to 0.5 pb at the 95% CL depending on event topology. In addition, the results are interpreted in several benchmark models in the context of supersymmetry with a new light dark sector exploring previously inaccessible parameter space.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: 44Citation - Scopus: 36Jet Production Rates in Association With W and Z Bosons in Pp Collisions at ?s = 7 Tev(Springer Verlag, 2012) Karapınar, Güler; Demir, Durmuş AliMeasurements of jet production rates in association with W and Z bosons for jet transverse momenta above 30 GeV are reported, using a sample of proton-proton collision events recorded by CMS at √s = 7TeV, corresponding to an integrated luminosity of 36 pb -1. The study includes the measurement of the normalized inclusive rates of jets σ(V+ ≥ n jets)=σ(V), where V represents either a W or a Z. In addition, the ratio of W to Z cross sections and the W charge asymmetry as a function of the number of associated jets are measured. A test of scaling at √s = 7TeV is also presented. The measurements provide a stringent test of perturbative-QCD calculations and are sensitive to the possible presence of new physics. The results are in agreement with the predictions of a simulation that uses explicit matrix element calculations for final states with jets. © 2012 SISSA.Article Citation - WoS: 11Citation - Scopus: 18Forward Energy Flow, Central Charged-Particle Multiplicities, and Pseudorapidity Gaps in W and Z Boson Events From Pp Collisions at ?s = 7 Tev(Springer Verlag, 2012) Demir, Durmuş Ali; Karapınar, GülerA study of forward energy flow and central charged-particle multiplicity in events with W and Z bosons decaying into leptons is presented. The analysis uses a sample of 7 TeV pp collisions, corresponding to an integrated luminosity of 36 pb-1, recorded by the CMS experiment at the LHC. The observed forward energy depositions, their correlations, and the central charged-particle multiplicities are not well described by the available non-diffractive soft-hadron production models. A study of about 300 events with no significant energy deposited in one of the forward calorimeters, corresponding to a pseudorapidity gap of at least 1. 9 units, is also presented. An indication for a diffractive component in these events comes from the observation that the majority of the charged leptons from the W(Z) decays are found in the hemisphere opposite to the gap. When fitting the signed lepton pseudorapidity distribution of these events with predicted distributions from an admixture of diffractive (pompyt) and non-diffractive (pythia) Monte Carlo simulations, the diffractive component is determined to be (50. 0 ± 9. 3 (stat.) ± 5. 2 (syst.))%. © 2012 CERN for the benefit of the CMS collaboration.