PubMed İndeksli Yayınlar Koleksiyonu / PubMed Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7645
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Article Citation - WoS: 15Citation - Scopus: 21Measurements of the Electroweak Diboson Production Cross Sections in Proton-Proton Collisions at Root S=5.02 Tev Using Leptonic Decays(American Physical Society, 2021) Karapınar, Güler; CMS CollaborationThe first measurements of diboson production cross sections in proton-proton interactions at a center-of-mass energy of 5.02 TeV are reported. They are based on data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 302 pb(-1). Events with two, three, or four charged light leptons (electrons or muons) in the final state are analyzed. The WW, WZ, and ZZ total cross sections are measured as sigma(WW) = 37:0(-5.2)(+5.5) (stat)(-2.6)(+2.7) (syst) pb, sigma(WZ) = 6.4(-2.1)(+2.5) (stat)(-0.3)(+0.5)(syst) pb, and sigma(ZZ) = 5.3(-2.1)(+2.5)(stat)(-0.4)(+0.5) (syst) pb. All measurements are in good agreement with theoretical calculations at combined next-to-next-to-leading order quantum chromodynamics and next-to-leading order electroweak accuracy.Article Citation - WoS: 32Citation - Scopus: 42Search for Long-Lived Particles Decaying in the Cms End Cap Muon Detectors in Proton-Proton Collisions at Root S=13 Tev(American Physical Society, 2021) Karapınar, Güler; CMS CollaborationA search for long-lived particles (LLPs) produced in decays of standard model (SM) Higgs bosons is presented. The data sample consists of 137 fb(-1) of proton-proton collisions at root s = 13 TeV, recorded at the LHC in 2016-2018. A novel technique is employed to reconstruct decays of LLPs in the end cap muon detectors. The search is sensitive to a broad range of LLP decay modes and to masses as low as a few GeV. No excess of events above the SM background is observed. The most stringent limits to date on the branching fraction of the Higgs boson to LLPs subsequently decaying to quarks and tau(+)tau(-) are found for proper decay lengths greater than 6, 20, and 40 m, for LLP masses of 7, 15, and 40 GeV, respectively.Article Citation - WoS: 6Citation - Scopus: 9Search for Pair-Produced Resonances Each Decaying Into at Least Four Quarks in Proton-Proton Collisions at Root S=13 Tev(American Physical Society, 2018) Sirunyan, A. M.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Karapınar, Güler; CMS CollaborationThis Letter presents the results of a search for pair-produced particles of masses above 100 GeV that each decay into at least four quarks. Using data collected by the CMS experiment at the LHC in 2015-2016, corresponding to an integrated luminosity of 38.2 fb(-1), reconstructed particles are clustered into two large jets of similar mass, each consistent with four-parton substructure. No statistically significant excess of data over the background prediction is observed in the distribution of average jet mass. Pair-produced squarks with dominant hadronic R-parity-violating decays into four quarks and with masses between 0.10 and 0.72 TeV are excluded at 95% confidence level. Similarly, pair-produced gluinos that decay into five quarks are also excluded with masses between 0.10 and 1.41 TeV at 95% confidence level. These are the first constraints that have been placed on pair-produced particles with masses below 400 GeV that decay into four or five quarks, bridging a significant gap in the coverage of R-parity-violating supersymmetry parameter space.Article Citation - WoS: 35Citation - Scopus: 58Observation of Medium-Induced Modifications of Jet Fragmentation in Pb-Pb Collisions at Root S(nn)=5.02 Tev Using Isolated Photon-Tagged Jets(American Physical Society, 2018) Karapınar, GülerMeasurements of fragmentation functions for jets associated with an isolated photon are presented for the first time in pp and Pb-Pb collisions. The analysis uses data collected with the CMS detector at the CERN LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Fragmentation functions are obtained for jets with P-T(jet) 30 GeV/c in events containing an isolated photon with p(T)(gamma) 60 GeV/c, using charged tracks with transverse momentum p(T)(trk) > 1 GeV/c in a cone around the jet axis. The association with an isolated photon constrains the initial p(T) and azimuthal angle of the parton whose shower produced the jet. For central Pb-Pb collisions, modifications of the jet fragmentation functions are observed when compared to those measured in pp collisions, while no significant differences are found in the 50% most peripheral collisions. Jets in central Pb-Pb events show an excess (depletion) of low (high) p(T) particles, with a transition around 3 GeV/c. This measurement shows for the first time the in-medium shower modifications of partons (quark dominated) with well-defined initial kinematics. It constitutes a new well-controlled reference for testing theoretical models of the parton passage through the quark-gluon plasma.Article Citation - WoS: 114Citation - Scopus: 63Search for Leptoquarks Coupled To Third-Generation Quarks in Proton-Proton Collisions at Root S=13 Tev(American Physical Society, 2018) Karapınar, Güler; CMS CollaborationThree of the most significant measured deviations from standard model predictions, the enhanced decay rate for B -> D-(*())tau nu, hints of lepton universality violation in B -> K-(*())ll decays, and the anomalous magnetic moment of the muon, can be explained by the existence of leptoquarks (LQs) with large couplings to third-generation quarks and masses at the TeV scale. The existence of these states can be probed at the LHC in high energy proton-proton collisions. A novel search is presented for pair production of LQs coupled to a top quark and a muon using data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1), recorded by the CMS experiment. No deviation from the standard model prediction has been observed and scalar LQs decaying exclusively into t mu are excluded up to masses of 1420 GeV. The results of this search are combined with those from previous searches for LQ decays into t tau and b nu, which excluded scalar LQs below masses of 900 and 1080 GeV. Vector LQs are excluded up to masses of 1190 GeV for all possible combinations of branching fractions to t mu, t tau and b nu. With this analysis, all relevant couplings of LQs with an electric charge of -1/3 to third-generation quarks are probed for the first time.Article Citation - WoS: 14Citation - Scopus: 30Evidence for the Associated Production of a Single Top Quark and a Photon in Proton-Proton Collisions at Root S=13 Tev(American Physical Society, 2018) Karapınar, Güler; CMS CollaborationThe first evidence of events consistent with the production of a single top quark in association with a photon is reported. The analysis is based on proton-proton collisions at root s = 13 TeV and recorded by the CMS experiment in 2016, corresponding to an integrated luminosity of 35.9 fb(-1). Events are selected by requiring the presence of a muon (mu), a photon (gamma), an imbalance in transverse momentum from an undetected neutrino (nu), and at least two jets (j) of which exactly one is identified as associated with the hadronization of a b quark. A multivariate discriminant based on topological and kinematic event properties is employed to separate signal from background processes. An excess above the backgroundonly hypothesis is observed, with a significance of 4.4 standard deviations. A fiducial cross section is measured for isolated photons with transverse momentum greater than 25 GeV in the central region of the detector. The measured product of the cross section and branching fraction is sigma(pp -> t gamma j) B (t -> mu nu b) = 115 +/- 17 (stat) +/- 30(syst) fb, which is consistent with the standard model prediction.Article Citation - WoS: 29Citation - Scopus: 35Search for Dark Matter Particles Produced in Association With a Top Quark Pair at Root S=13 Tev(American Physical Society, 2019) Karapınar, Güler; CMS CollaborationA search is performed for dark matter particles produced in association with a top quark pair in proton-proton collisions at root s = 13 TeV. The data correspond to an integrated luminosity of 35.9 fb(-1) recorded by the CMS detector at the LHC. No significant excess over the standard model expectation is observed. The results are interpreted using simplified models of dark matter production via spin-0 mediators that couple to dark matter particles and to standard model quarks, providing constraints on the coupling strength between the mediator and the quarks. These are the most stringent collider limits to date for scalar mediators, and the most stringent for pseudoscalar mediators at low masses.Article Citation - WoS: 44Citation - Scopus: 65Search for the Higgs Boson Decaying To Two Muons in Proton-Proton Collisions at Root S=13 Tev(American Physical Society, 2019) Karapınar, Güler; CMS CollaborationA search for the Higgs boson decaying to two oppositely charged muons is presented using data recorded by the CMS experiment at the CERN LHC in 2016 at a center-of-mass energy root s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). Data are found to be compatible with the predicted background. For a Higgs boson with a mass of 125.09 GeV, the 95% confidence level observed (background-only expected) upper limit on the production cross section times the branching fraction to a pair of muons is found to be 3.0 (2.5) times the standard model expectation. In combination with data recorded at center-of-mass energies root s = 7 and 8 TeV, the background-only expected upper limit improves to 2.2 times the standard model value with a standard model expected significance of 1.0 standard deviation. The corresponding observed upper limit is 2.9 with an observed significance of 0.9 standard deviation. This corresponds to an observed upper limit on the standard model Higgs boson branching fraction to muons of 6.4 x 10(-4) and to an observed signal strength of 1.0 +/- 1.0(stat) +/- 0.1(syst).Article Citation - WoS: 58Citation - Scopus: 147Combination of Searches for Higgs Boson Pair Production in Proton-Proton Collisions at Root S=13 Tev(American Physical Society, 2019) Karapınar, Güler; CMS CollaborationThis Letter describes a search for Higgs boson pair production using the combined results from four final states: bb gamma gamma, bb tau tau, bbbb, and bbVV, where V represents a W or Z boson. The search is performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions at root s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). Limits are set on the Higgs boson pair production cross section. A 95% confidence level observed (expected) upper limit on the non-resonant production cross section is set at 22.2 (12.8) times the standard model value. A search for narrow resonances decaying to Higgs boson pairs is also performed in the mass range 250-3000 GeV. No evidence for a signal is observed, and upper limits are set on the resonance production cross section.Article Citation - WoS: 4Citation - Scopus: 8Search for Narrow H Gamma Resonances in Proton-Proton Collisions at Root S=13 Tev(American Physical Society, 2019) Karapınar, Güler; CMS CollaborationA search for heavy, narrow resonances decaying to a Higgs boson and a photon (Hy) has been performed in proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb-1 collected with the CMS detector at the LHC in 2016. Events containing a photon and a Lorentz-boosted hadronically decaying Higgs boson reconstructed as a single, large-radius jet are considered, and the y jet invariant mass spectrum is analyzed for the presence of narrow resonances. To increase the sensitivity of the search, events are categorized depending on whether or not the large-radius jet can be identified as a result of the merging of two jets originating from b quarks. Results in both categories are found to agree with the predictions of the standard model. Upper limits on the production rate of Hy resonances are sct as a function of their mass in the range of 720-3250 GeV, representing thc most stringent constraints to date.