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: 25Citation - Scopus: 32Using Z Boson Events To Study Parton-Medium Interactions in Pb-Pb Collisions(American Physical Society, 2022) Karapınar, GülerThe spectra measurements of charged hadrons produced in the shower of a parton originating in the same hard scattering with a leptonically decaying Z boson arc reported in lead-lead nuclei (Pb-Pb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Both Pb-Pb and pp data sets are recorded by the CMS experiment at the LHC and correspond to an integrated luminosity of 1.7 nb(-1) and 320 pb(-1), respectively. Hadronic collision data with one reconstructed Z boson candidate with the transverse momentum p(T) > 30 GeV/c are analyzed. The Z boson constrains the initial energy and direction of the associated parton. In heavy ion events, azimuthal angular distributions of charged hadrons with respect to the direction of a Z boson are sensitive to modifications of the in-medium parton shower and medium response. compared to reference data from pp interactions, the results for central Pb-Pb collisions indicate a modification of the angular correlations. The measurements of the fragmentation functions and p(T) spectra of charged particles in Z boson events, which are sensitive to medium modifications of the parton shower longitudinal structure, are also reported. Significant modifications in central Pb-Pb events compared to the pp reference data are also found for these observables.Article Citation - WoS: 13Citation - Scopus: 20Measurement of Double-Parton Scattering in Inclusive Production of Four Jets With Low Transverse Momentum in Proton-Proton Collisions at Root S=13 Tev(Springer, 2022) Tumasyan, A.; Karapınar, GülerA measurement of inclusive four-jet production in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. The transverse momenta of jets within vertical bar eta vertical bar 4.7 are required to exceed 35, 30, 25, and 20 GeV for the first-, second-, third-, and fourth-leading jet, respectively. Differential cross sections are measured as functions of the jet transverse momentum, jet pseudorapidity, and several other observables that describe the angular correlations between the jets. The measured distributions show sensitivity to different aspects of the underlying event, parton shower modeling, and matrix element calculations. In particular, the interplay between angular correlations caused by parton shower and double-parton scattering contributions is shown to be important. The double-parton scattering contribution is extracted by means of a template fit to the data, using distributions for single-parton scattering obtained from Monte Carlo event generators and a double-parton scattering distribution constructed from inclusive single-jet events in data. The effective double-parton scattering cross section is calculated and discussed in view of previous measurements and of its dependence on the models used to describe the single-parton scattering background.Article Citation - WoS: 16Citation - Scopus: 16Dependence of Inclusive Jet Production on the Anti-K(t) Distance Parameter in Pp Collisions at Root S=13 Tev(Springer, 2020) CMS Collaboration; Karapınar, GülerThe dependence of inclusive jet production in proton-proton collisions with a center-of-mass energy of 13 TeV on the distance parameter R of the anti-k(T) algorithm is studied using data corresponding to integrated luminosities up to 35.9 fb(-1) collected by the CMS experiment in 2016. The ratios of the inclusive cross sections as functions of transverse momentum p(T) and rapidity y, for R in the range 0.1 to 1.2 to those using R = 0.4 are presented in the region 84 < p(T)< 1588 GeV and |y|< 2.0. The results are compared to calculations at leading and next-to-leading order in the strong coupling constant using different parton shower models. The variation of the ratio of cross sections with R is well described by calculations including a parton shower model, but not by a leading-order quantum chromodynamics calculation including nonperturbative effects. The agreement between the data and the theoretical predictions for the ratios of cross sections is significantly improved when next-to-leading order calculations with nonperturbative effects are used.Article Citation - WoS: 70Citation - Scopus: 59First Measurement of Large Area Jet Transverse Momentum Spectra in Heavy-Ion Collisions(Springer Science and Business Media Deutschland GmbH, 2021) Karapınar, Güler; CMS CollaborationJet production in lead-lead (PbPb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV is studied with the CMS detector at the LHC, using PbPb and pp data samples corresponding to integrated luminosities of 404 ?b?1 and 27.4 pb?1, respectively. Jets with different areas are reconstructed using the anti-kT algorithm by varying the distance parameter R. The measurements are performed using jets with transverse momenta (pT) greater than 200 GeV and in a pseudorapidity range of |?| < 2. To reveal the medium modification of the jet spectra in PbPb collisions, the properly normalized ratio of spectra from PbPb and pp data is used to extract jet nuclear modification factors as functions of the PbPb collision centrality, pT and, for the first time, as a function of R up to 1.0. For the most central collisions, a strong suppression is observed for high-pT jets reconstructed with all distance parameters, implying that a significant amount of jet energy is scattered to large angles. The dependence of jet suppression on R is expected to be sensitive to both the jet energy loss mechanism and the medium response, and so the data are compared to several modern event generators and analytic calculations. The models considered do not fully reproduce the data. [Figure not available: see fulltext.] © 2021, The Author(s).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.Article Citation - WoS: 30Citation - Scopus: 28Measurement of Quark- and Gluon-Like Jet Fractions Using Jet Charge in Pbpb and Pp Collisions at 5.02 Tev(Springer Verlag, 2020) CMS Collaboration; Karapınar, GülerThe momentum-weighted sum of the electric charges of particles inside a jet, known as jet charge, is sensitive to the electric charge of the particle initiating the parton shower. This paper presents jet charge distributions in root sNN = 5.02 TeV lead-lead (PbPb) and proton-proton (pp) collisions recorded with the CMS detector at the LHC. These data correspond to integrated luminosities of 404 mu b(-1)and 27.4 pb(-1)for PbPb and pp collisions, respectively. Leveraging the sensitivity of the jet charge to fundamental differences in the electric charges of quarks and gluons, the jet charge distributions from simulated events are used as templates to extract the quark- and gluon-like jet fractions from data. The modification of these jet fractions is examined by comparing pp and PbPb data as a function of the overlap of the colliding Pb nuclei (centrality). This measurement tests the color charge dependence of jet energy loss due to interactions with the quark-gluon plasma. No significant modification between different centrality classes and with respect to pp results is observed in the extracted quark- and gluon-like jet fractions.Article Citation - WoS: 10Citation - Scopus: 29Event Shape Variables Measured Using Multijet Final States in Proton-Proton Collisions at Root S=13 Tev(Springer Verlag, 2018) Karapınar, Güler; CMS CollaborationThe study of global event shape variables can provide sensitive tests of predictions for multijet production in proton-proton collisions. This paper presents a study of several event shape variables calculated using jet four momenta in proton-proton collisions at a centre-of-mass energy of 13 TeV and uses data recorded with the CMS detector at the LHC corresponding to an integrated luminosity of 2.2 fb(-1). After correcting for detector effects, the resulting distributions are compared with several theoretical predictions. The agreement generally improves as the energy, represented by the average transverse momentum of the two leading jets, increases.Article Citation - WoS: 16Citation - Scopus: 36Search for Production of Higgs Boson Pairs in the Four B Quark Final State Using Large-Area Jets in Proton-Proton Collisions at Root S 13 Tev(Springer Verlag, 2019) Karapınar, Güler; CMS CollaborationA search is presented for pair production of the standard model Higgs boson using data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected by the CMS experiment at the CERN LHC in 2016, and corresponding to an integrated luminosity of 35.9 fb(-1). The final state consists of two b quark-antiquark pairs. The search is conducted in the region of phase space where one pair is highly Lorentz-boosted and is reconstructed as a single large-area jet, and the other pair is resolved and is reconstructed using two b-tagged jets. The results are obtained by combining this analysis with another from CMS looking for events with two large jets. Limits are set on the product of the cross sections and branching fractions for narrow bulk gravitons and radions in warped extradimensional models having a mass in the range 750-3000 GeV. The resulting observed and expected upper limits on the non-resonant Higgs boson pair production cross section correspond to 179 and 114 times the standard model value, respectively, at 95% confidence level. The existence of anomalous Higgs boson couplings is also investigated and limits are set on the non-resonant Higgs boson pair production cross sections for representative coupling values.Article Citation - WoS: 10Citation - Scopus: 14Measurement of Inclusive Very Forward Jet Cross Sections in Proton-Lead Collisions at P Snn=5:02 Tev(Springer Verlag, 2019) Karapınar, Güler; CMS CollaborationMeasurements of di ff erential cross sections for inclusive very forward jet production in proton-lead collisions as a function of jet energy are presented. The data were collected with the CMS experiment at the LHC in the laboratory pseudorapidity range 6 : 6 < < 5 : 2. Asymmetric beam energies of 4TeV for protons and 1.58TeV per nucleon for Pb nuclei were used, corresponding to a center-of-mass energy per nucleon pair of p sNN = 5 : 02TeV. Collisions with either the proton (p+ Pb) or the ion (Pb+ p) traveling towards the negative hemisphere are studied. The jet cross sections are unfolded to stable-particle level cross sections with pT & 3 GeV, and compared to predictions from various Monte Carlo event generators. In addition, the cross section ratio of p+ Pb and Pb+ p data is presented. The results are discussed in terms of the saturation of gluon densities at low fractional parton momenta. None of the models under consideration describes all the data over the full jet-energy range and for all beam con fi gurations. Discrepancies between the di ff erential cross sections in data and model predictions of more than two orders of magnitude are observed.Article Citation - WoS: 137Citation - Scopus: 174Search for Narrow and Broad Dijet Resonances in Proton-Proton Collisions at ?s=13 Tev and Constraints on Dark Matter Mediators and Other New Particles(Springer, 2018) CMS Collaboration; Karapınar, GülerSearches for resonances decaying into pairs of jets are performed using proton-proton collision data collected at s=13 TeV corresponding to an integrated luminosity of up to 36 fb−1. A low-mass search, for resonances with masses between 0.6 and 1.6 TeV, is performed based on events with dijets reconstructed at the trigger level from calorimeter information. A high-mass search, for resonances with masses above 1.6 TeV, is performed using dijets reconstructed offline with a particle-flow algorithm. The dijet mass spectrum is well described by a smooth parameterization and no evidence for the production of new particles is observed. Upper limits at 95% confidence level are reported on the production cross section for narrow resonances with masses above 0.6 TeV. In the context of specific models, the limits exclude string resonances with masses below 7.7 TeV, scalar diquarks below 7.2 TeV, axigluons and colorons below 6.1 TeV, excited quarks below 6.0 TeV, color-octet scalars below 3.4 TeV, W′ bosons below 3.3 TeV, Z′ bosons below 2.7 TeV, Randall-Sundrum gravitons below 1.8 TeV and in the range 1.9 to 2.5 TeV, and dark matter mediators below 2.6 TeV. The limits on both vector and axial-vector mediators, in a simplified model of interactions between quarks and dark matter particles, are presented as functions of dark matter particle mass and coupling to quarks. Searches are also presented for broad resonances, including for the first time spin-1 resonances with intrinsic widths as large as 30% of the resonance mass. The broad resonance search improves and extends the exclusions of a dark matter mediator to larger values of its mass and coupling to quarks.
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