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: 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.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: 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.Article Citation - WoS: 22Citation - Scopus: 103Search for Heavy Higgs Bosons Decaying To a Top Quark Pair in Proton-Proton Collisions at Root S=13 Tev(Springer Verlag, 2020) ; CMS Collaboration; Karapınar, GülerA search is presented for additional scalar (H) or pseudoscalar (A) Higgs bosons decaying to a top quark pair in proton-proton collisions at a center-of-mass energy of 13 TeV. The data set analyzed corresponds to an integrated luminosity of 35.9 fb(-1) collected by the CMS experiment at the LHC. Final states with one or two charged leptons are considered. The invariant mass of the reconstructed top quark pair system and variables that are sensitive to the spin of the particles decaying into the top quark pair are used to search for signatures of the H or A bosons. The interference with the standard model top quark pair background is taken into account. A moderate signal-like deviation compatible with an A boson with a mass of 400 GeV is observed with a global significance of 1.9 standard deviations. New stringent constraints are reported on the strength of the coupling of the hypothetical bosons to the top quark, with the mass of the bosons ranging from 400 to 750 GeV and their total relative width from 0.5 to 25%. The results of the search are also interpreted in a minimal supersymmetric standard model scenario. Values of m(A) from 400 to 700 GeV are probed, and a region with values of tan beta below 1.0 to 1.5, depending on m(A), is excluded at 95% confidence level.Article Citation - WoS: 17Citation - Scopus: 39Measurement of the Cross Section for T(t)over-Bar Production With Additional Jets and B Jets in Pp Collisions at Root S=13tev(Springer Verlag, 2020) CMS Collaboration; Karapınar, GülerMeasurements of the cross section for the production of top quark pairs in association with a pair of jets from bottom quarks (sigma(t (t) over barb (b) over bar)) and in association with a pair of jets from quarks of any flavor or gluons (sigma(t (t) over bar jj)) and their ratio are presented. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV by the CMS experiment at the LHC in 2016 and correspond to an integrated luminosity of 35.9 fb(-1). The measurements are performed in a fiducial phase space and extrapolated to the full phase space, separately for the dilepton and lepton+jets channels, where lepton corresponds to either an electron or a muon. The results of the measurements in the fiducial phase space for the dilepton and lepton+jets channels, respectively, are sigma(t (t) over bar jj) = 2.36 +/- 0.02 (stat)+/- 0.20 (syst) pb and 31.0 +/- 0.2 (stat)+/- 2.9 (syst) pb, and for the cross section ratio 0.017 +/- 0.001 (stat)+/- 0.001 (syst) and 0.020 +/- 0.001 (stat)+/- 0.001 (syst). The values of sigma(t (t) over barb (b) over bar) are determined from the product of the sigma(t (t) over bar jj) and the cross section ratio, obtaining, respectively, 0.040 +/- 0.002 (stat)+/- 0.005 (syst) pb and 0.62 +/- 0.03 (stat)+/- 0.07 (syst) pb. These measurements are the most precise to date and are consistent, within the uncertainties, with the standard model expectations obtained using a matrix element calculation at next-to-leading order in quantum chromodynamics matched to a parton shower.