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: 80Citation - Scopus: 74Measurements of Differential and Double-Differential Drell-Yan Cross Sections in Proton-Proton Collisions at ?s=8 Tev(Springer Verlag, 2015) Karapınar, Güler; CMS CollaborationMeasurements of the differential and double-differential Drell-Yan cross sections in the dielectron and dimuon channels are presented. They are based on proton-proton collision data at root s = 8 TeV recorded with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb(-1). The measured inclusive cross section in the Z peak region (60-120 GeV), obtained from the combination of the dielectron and dimuon channels, is 1138 +/- 8 (exp) +/- 25 (theo) +/- 30 (lumi) pb, where the statistical uncertainty is negligible. The differential cross section d sigma/dm in the dilepton mass range 15-2000 GeV is measured and corrected to the full phase space. The double-differential cross section d(2)sigma/dm d vertical bar y vertical bar is also measured over the mass range 20 to 1500 GeV and absolute dilepton rapidity from 0 to 2.4. In addition, the ratios of the normalized differential cross sections measured at root s = 7 and 8 TeV are presented. These measurements are compared to the predictions of perturbative QCD at next-to-leading and next-to-next-to-leading (NNLO) orders using various sets of parton distribution functions (PDFs). The results agree with the NNLO theoretical predictions computed with FEWZ 3.1 using the CT10 NNLO and NNPDF2.1 NNLO PDFs. The measured double-differential cross section and ratio of normalized differential cross sections are sufficiently precise to constrain the proton PDFs.Article Citation - WoS: 47Citation - Scopus: 39Search for Decays of Stopped Long-Lived Particles Produced in Proton-Proton Collisions at ?s=8tev(Springer Verlag, 2015) Karapınar, Güler; CMS CollaborationA search has been performed for long-lived particles that could have come to rest within the CMS detector, using the time intervals between LHC beam crossings. The existence of such particles could be deduced from observation of their decays via energy deposits in the CMS calorimeter appearing at times that are well separated from any proton-proton collisions. Using a data set corresponding to an integrated luminosity of 18.6 fb(-1) of 8 TeV proton-proton collisions, and a search interval corresponding to 281 h of trigger livetime, 10 events are observed, with a background prediction of 13.2(-2.5)(+3.6) events. Limits are presented at 95 % confidence level on gluino and top squark production, for over 13 orders of magnitude in the mean proper lifetime of the stopped particle. Assuming a cloud model of R-hadron interactions, a gluino with mass less than or similar to 1000 GeV and a top squark with mass less than or similar to 525 GeV are excluded, for lifetimes between 1 mu s and 1000 s. These results are the most stringent constraints on stopped particles to date.Article Citation - WoS: 518Citation - Scopus: 550Precise Determination of the Mass of the Higgs Boson and Tests of Compatibility of Its Couplings With the Standard Model Predictions Using Proton Collisions at 7 and 8 Tev(Springer Nature, 2015) Khachatryan, V.; Sirunyan, A.M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; Janot, P.Properties of the Higgs boson with mass near 125 GeV are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. The decay channels include γγ, ZZ, WW, ττ, bb, and μμ pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1fb-1at 7TeV and up to 19.7fb-1at 8 TeV. From the high-resolution γγ and ZZ channels, the mass of the Higgs boson is determined to be (Formula presented) GeV. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model expectation is (Formula presented) at the measured mass. The couplings of the Higgs boson are probed for deviations in magnitude from the standard model predictions in multiple ways, including searches for invisible and undetected decays. No significant deviations are found. © 2015, CERN for the benefit of the CMS collaboration.Article Citation - WoS: 62Citation - Scopus: 45Nuclear Effects on the Transverse Momentum Spectra of Charged Particles in Ppb Collisions at ?s(nn)=5.02 Tev(Springer Verlag, 2015) Karapınar, Güler; CMS CollaborationTransverse momentum spectra of charged particles are measured by the CMS experiment at the CERN LHC in pPb collisions at root s(NN) = 5.02 TeV, in the range 0.4 < pT < 120 GeV/c and pseudorapidity |eta(CM)| < 1.8 in the proton-nucleon center-of-mass frame. For p(T) < 10 GeV/c, the charged-particle production is asymmetric about eta(CM) = 0, with smaller yield observed in the direction of the proton beam, qualitatively consistent with expectations from shadowing in nuclear parton distribution functions (nPDF). A pp reference spectrum at root s = 5.02 TeV is obtained by interpolation from previous measurements at higher and lower center-of-mass energies. The p(T) distribution measured in pPb collisions shows an enhancement of charged particles with p(T) > 20 GeV/c compared to expectations from the pp reference. The enhancement is larger than predicted by perturbative quantum chromodynamics calculations that include antishadowing modifications of nPDFs.Article Citation - WoS: 69Citation - Scopus: 65Search for a Standard Model Higgs Boson Produced in Association With a Top-Quark Pair and Decaying To Bottom Quarks Using a Matrix Element Method(Springer Verlag, 2015) Karapınar, Güler; CMS CollaborationA search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks is presented. Events with hadronic jets and one or two oppositely charged leptons are selected from a data sample corresponding to an integrated luminosity of 19.5 fb(-1) collected by the CMS experiment at the LHC in pp collisions at a centre-of-mass energy of 8 TeV. In order to separate the signal from the larger t (t) over bar + jets background, this analysis uses a matrix element method that assigns a probability density value to each reconstructed event under signal or background hypotheses. The ratio between the two values is used in a maximum likelihood fit to extract the signal yield. The results are presented in terms of the measured signal strength modifier, mu, relative to the standard model prediction for a Higgs boson mass of 125 GeV. The observed (expected) exclusion limit at a 95% confidence level is mu < 4.2 (3.3), corresponding to a best fit value <(mu)over cap> = 1.2(-1.5)(+1.6).Article Citation - WoS: 4Citation - Scopus: 8Distributions of Topological Observables in Inclusive Three- and Four-Jet Events in Pp Collisions at ?s=7 Tev(Springer Verlag, 2015) Karapınar, Güler; CMS CollaborationThis paper presents distributions of topological observables in inclusive three- and four-jet events produced in pp collisions at a centre-of-mass energy of 7 TeV with a data sample collected by the CMS experiment corresponding to a luminosity of 5.1 fb(-1). The distributions are corrected for detector effects, and compared with several event generators based on two- and multi-parton matrix elements at leading order. Among the considered calculations, MadGraph interfaced with PYTHIA6 displays the overall best agreement with data.Article Citation - WoS: 44Citation - Scopus: 38Constraints on the Pmssm, Amsb Model and on Other Models From the Search for Long-Lived Charged Particles in Proton-Proton Collisions at ?s = 8 Tev(Springer Verlag, 2015) Karapınar, Güler; CMS CollaborationStringent limits are set on the long-lived lepton-like sector of the phenomenological minimal supersymmetric standard model (pMSSM) and the anomaly-mediated super-symmetry breaking (AMSB) model. The limits are derived from the results presented in a recent search for long-lived charged particles in proton-proton collisions, based on data collected by the CMS detector at a centre-of-mass energy of 8 TeV at the Large Hadron Collider. In the pMSSM parameter sub-space considered, 95.9% of the points predicting charginos with a lifetime of at least 10 ns are excluded. These constraints on the pMSSM are the first obtained at the LHC. Charginos with a lifetime greater than 100 ns and masses up to about 800 GeV in the AMSB model are also excluded. The method described can also be used to set constraints on other models.Article Citation - WoS: 34Citation - Scopus: 29Measurements of the Zz Production Cross Sections in the 2l2 Nu Channel in Proton-Proton Collisions at ?s=7 and 8 Tev and Combined Constraints on Triple Gauge Couplings(Springer Verlag, 2015) Karapınar, Güler; CMS CollaborationMeasurements of the ZZ production cross sections in proton-proton collisions at center-of-mass energies of 7 and 8 TeV are presented. Candidate events for the leptonic decay mode ZZ -> 2l2 nu. where l denotes an electron or a muon, are reconstructed and selected from data corresponding to an integrated luminosity of 5.1 (19.6) fb(-1) at 7 (8) TeV collected with the CMS experiment. The measured cross sections, sigma(pp -> ZZ) = 5.1(1.4)(+1.5) (stat)(-1.1)(+1.4) (syst) +/- 0.1 (lumi) pb at 7 TeV, and 7.2(-0.8)(+0.8) (stat)(1.5)(+1.9) (syst) +/- 0.2 (lumi) pb at 8 TeV, are in good agreement with the standard model predictions with next-to-leading-order accuracy. The selected data are analyzed to search for anomalous triple gauge couplings involving the ZZ final state. In the absence of any deviation from the standard model predictions, limits are set on the relevant parameters. These limits are then combined with the previously published CMS results for ZZ in 4l final states, yielding the most stringent constraints on the anomalous couplings.Correction Citation - WoS: 32Citation - Scopus: 5Measurement of B Hadron Lifetimes in Pp Collisions at Root S = 8tev (vol 78, 2018)(Springer Verlag, 2018) Karapınar, Güler; CMS Collaboration[No abstract available]Article Citation - WoS: 6Citation - Scopus: 9Studies of Inclusive Four-Jet Production With Two B-Tagged Jets in Proton-Proton Collisions at 7 Tev(American Physical Society, 2016) Karapınar, Güler; CMS CollaborationMeasurements are presented of the cross section for the production of at least four jets, of which at least two originate from b quarks, in proton-proton collisions. Data collected with the CMS detector at the LHC at a center-of-mass energy of 7 TeV are used, corresponding to an integrated luminosity of 3 pb(-1). The cross section is measured as a function of the jet transverse momentum for p(T) > 20 GeV, and of the jet pseudorapidity for |eta| < 2.4 (b jets), 4.7 (untagged jets). The correlations in azimuthal angle and pT between the jets are also studied. The inclusive cross section is measured to be sigma(pp -> 2b + 2j + X) = 69 +/- 3(stat) +/- 24(syst) nb. The eta and p(T) distributions of the four jets and the correlations between them are well reproduced by event generators that combine perturbative QCD calculations at next-to-leading-order accuracy with contributions from parton showers and multiparton interactions.