Rectorate / Rektörlük
Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
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Article Citation - WoS: 76Citation - Scopus: 88Search for a Standard Model-Like Higgs Boson in the Mu(+)mu(-) and E(+)e(-) Decay Channels at the Lhc(Elsevier Ltd., 2015) Karapınar, GülerA search is presented for a standard model-like Higgs boson decaying to the mu(+)mu(-) or e(+)e(-) final states based on proton-proton collisions recorded by the CMS experiment at the CERN LHC. The data correspond to integrated luminosities of 5.0 fb(-1) at a centre-of-mass energy of 7 TeV and 19.7 fb(-1) at 8 TeV for the mu(+)mu(-) search, and of 19.7 fb(-1) at 8 TeV for the e(+)e(-) search. Upper limits on the production cross section times branching fraction at the 95% confidence level are reported for Higgs boson masses in the range from 120 to 150 GeV. For a Higgs boson with a mass of 125 GeV decaying to mu(+)mu(-), the observed (expected) upper limit on the production rate is found to be 7.4 (6.5(-1.9)(+2.8)) times the standard model value. This corresponds to an upper limit on the branching fraction of 0.0016. Similarly, for e(+)e(-), an upper limit of 0.0019 is placed on the branching fraction, which is approximate to 3.7 x 10(5) times the standard model value. These results, together with recent evidence of the 125 GeV boson coupling to tau-leptons with a larger branching fraction consistent with the standard model, confirm that the leptonic couplings of the new boson are not flavour-universal. (C) 2015 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V.Article Citation - WoS: 69Search for Higgs Boson Pair Production in the Gamma Gamma B(b)over-Bar Final State in Pp Collisions at Root S=13 Tev(Elsevier Ltd., 2019) Karapınar, Güler; CMS CollaborationA search is presented for the production of a pair of Higgs bosons, where one decays into two photons and the other one into a bottom quark-antiquark pair. The analysis is performed using proton-proton collision data at root s = 13 TeV recorded in 2016 by the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb(-1) . The results are in agreement with standard model (SM) predictions. In a search for resonant production, upper limits are set on the cross section for new spin-0 or spin-2 particles. For the SM-like nonresonant production hypothesis, the data exclude a product of cross section and branching fraction larger than 2.0 fb at 95% confidence level (CL), corresponding to about 24 times the SM prediction. Values of the effective Higgs boson self-coupling K X are constrained to be within the range -11 < K-lambda < 17 at 95% CL, assuming all other Higgs boson couplings are at their SM value. The constraints on K-lambda, are the most restrictive to date. (C) 2018 The Author(s). Published by Elsevier B.V.Article Citation - WoS: 38Citation - Scopus: 50Search for Light Pseudoscalar Boson Pairs Produced From Decays of the 125 Gev Higgs Boson in Final States With Two Muons and Two Nearby Tracks in Pp Collisions at Root S D=13tev(Elsevier Ltd., 2020) Karapınar, GülerA search is presented for pairs of light pseudoscalar bosons, in the mass range from 4 to 15 GeV, produced from decays of the 125 GeV Higgs boson. The decay modes considered are final states that arise when one of the pseudoscalars decays to a pair of tau leptons, and the other one either into a pair of tau leptons or muons. The search is based on proton-proton collisions collected by the CMS experiment in 2016 at a center-of-mass energy of 13 TeV that correspond to an integrated luminosity of 35.9 fb(-1). The 2 mu 2 tau and 4 tau channels are used in combination to constrain the product of the Higgs boson production cross section and the branching fraction into 4 tau final state, sigma beta, exploiting the linear dependence of the fermionic coupling strength of pseudoscalar bosons on the fermion mass. No significant excess is observed beyond the expectation from the standard model. The observed and expected upper limits at 95% confidence level on sigma beta, relative to the standard model Higgs boson production cross section, are set respectively between 0.022 and 0.23 and between 0.027 and 0.19 in the mass range probed by the analysis. (C) 2019 The Author(s). Published by Elsevier B.V.Article Citation - WoS: 54Citation - Scopus: 61Search for a Massive Resonance Decaying To a Pair of Higgs Bosons in the Four B Quark Final State in Proton–proton Collisions at S=13tev(Elsevier Ltd., 2018) CMS Collaboration; Karapınar, GülerA search for a massive resonance decaying into a pair of standard model Higgs bosons, in a final state consisting of two b quark–antiquark pairs, is performed. A data sample of proton–proton collisions at a centre-of-mass energy of 13 TeV is used, collected by the CMS experiment at the CERN LHC in 2016, and corresponding to an integrated luminosity of 35.9fb−1. The Higgs bosons are highly Lorentz-boosted and are each reconstructed as a single large-area jet. The signal is characterized by a peak in the dijet invariant mass distribution, above a background from the standard model multijet production. The observations are consistent with the background expectations, and are interpreted as upper limits on the products of the s-channel production cross sections and branching fractions of narrow bulk gravitons and radions in warped extra-dimensional models. The limits range from 126 to 1.4 fb at 95% confidence level for resonances with masses between 750 and 3000 GeV, and are the most stringent to date, over the explored mass range.Article Citation - WoS: 82Citation - Scopus: 100Evidence for the Higgs Boson Decay To a Bottom Quark–antiquark Pair(Elsevier Ltd., 2018) CMS Collaboration; Karapınar, GülerA search for the standard model (SM) Higgs boson (H) decaying to bb‾ when produced in association with an electroweak vector boson is reported for the following processes: Z(νν)H, W(μν)H, W(eν)H, Z(μμ)H, and Z(ee)H. The search is performed in data samples corresponding to an integrated luminosity of 35.9fb−1 at s=13TeV recorded by the CMS experiment at the LHC during Run 2 in 2016. An excess of events is observed in data compared to the expectation in the absence of a H→bb‾ signal. The significance of this excess is 3.3 standard deviations, where the expectation from SM Higgs boson production is 2.8. The signal strength corresponding to this excess, relative to that of the SM Higgs boson production, is 1.2±0.4. When combined with the Run 1 measurement of the same processes, the signal significance is 3.8 standard deviations with 3.8 expected. The corresponding signal strength, relative to that of the SM Higgs boson, is 1.06−0.29 +0.31.Article Citation - WoS: 97Citation - Scopus: 114Search for Higgs Boson Pair Production in Events With Two Bottom Quarks and Two Tau Leptons in Proton–proton Collisions at S=13tev(Elsevier Ltd., 2018) CMS Collaboration; Karapınar, GülerA search for the production of Higgs boson pairs in proton–proton collisions at a centre-of-mass energy of 13 TeV is presented, using a data sample corresponding to an integrated luminosity of 35.9fb−1 collected with the CMS detector at the LHC. Events with one Higgs boson decaying into two bottom quarks and the other decaying into two τ leptons are explored to investigate both resonant and nonresonant production mechanisms. The data are found to be consistent, within uncertainties, with the standard model background predictions. For resonant production, upper limits at the 95% confidence level are set on the production cross section for Higgs boson pairs as a function of the hypothesized resonance mass and are interpreted in the context of the minimal supersymmetric standard model. For nonresonant production, upper limits on the production cross section constrain the parameter space for anomalous Higgs boson couplings. The observed (expected) upper limit at 95% confidence level corresponds to about 30 (25) times the prediction of the standard model.Article Citation - WoS: 102Citation - Scopus: 103Search for Resonant Pair Production of Higgs Bosons Decaying To Two Bottom Quark-Antiquark Pairs in Proton-Proton Collisions at 8 Tev(Elsevier Ltd., 2015) CMS Collaboration; Karapınar, GülerA model-independent search for a narrow resonance produced in proton-proton collisions at s=8 TeV and decaying to a pair of 125 GeV Higgs bosons that in turn each decays into a bottom quark-antiquark pair is performed by the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 17.9 fb-1. No evidence for a signal is observed. Upper limits at a 95% confidence level on the production cross section for such a resonance, in the mass range from 270 to 1100 GeV, are reported. Using these results, a radion with decay constant of 1 TeV and mass from 300 to 1100 GeV, and a Kaluza-Klein graviton with mass from 380 to 830 GeV are excluded at a 95% confidence level. © 2015 The Authors.Article Citation - WoS: 144Citation - Scopus: 121Inclusive Search for a Vector-Like T Quark With Charge 2/3 in Pp Collisions at ?s=8 Tev(Elsevier Ltd., 2014) CMS Collaboration; Karapınar, GülerA search is performed for a massive new vector-like quark T, with charge 23, that is pair produced together with its antiparticle in proton-proton collisions. The data were collected by the CMS experiment at the Large Hadron Collider in 2012 at s=8TeV and correspond to an integrated luminosity of 19.5fb-1. The T quark is assumed to decay into three different final states, bW, tZ, and tH. The search is carried out using events with at least one isolated lepton. No deviations from standard model expectations are observed, and lower limits are set on the T quark mass at 95% confidence level. The lower limit lies between 687 and 782 GeV for all possible values of the branching fractions into the three different final states assuming strong production. These limits are the most stringent constraints to date on the existence of such a quark. © 2014 The Authors.Article Citation - WoS: 63Citation - Scopus: 51Search for Top-Squark Pairs Decaying Into Higgs or Z Bosons in Pp Collisions at S=8 Tev(Elsevier Ltd., 2014) CMS Collaboration; Karapınar, GülerA search for supersymmetry through the direct pair production of top squarks, with Higgs (H) or Z bosons in the decay chain, is performed using a data sample of proton-proton collisions at s=8 TeV collected in 2012 with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 19.5 fb-1. The search is performed using a selection of events containing leptons and bottom-quark jets. No evidence for a significant excess of events over the standard model background prediction is observed. The results are interpreted in the context of simplified supersymmetric models with pair production of a heavier top-squark mass eigenstate t~2 decaying to a lighter top-squark mass eigenstate t~1 via either t~2→Ht~1 or t~2→Zt~1, followed in both cases by t~1→tχ~10, where χ~10 is an undetected, stable, lightest supersymmetric particle. The interpretation is performed in the region where the mass difference between the t~1 and χ~10 states is approximately equal to the top-quark mass (mt~1-mχ~10≃mt), which is not probed by searches for direct t~1 squark pair production. The analysis excludes top squarks with masses mt~2<575 GeV and mt~1<400 GeV at a 95% confidence level. © 2014 The Authors.Article Citation - WoS: 152Citation - Scopus: 142Constraints on the Higgs Boson Width From Off-Shell Production and Decay To Z-Boson Pairs(Elsevier Ltd., 2014) CMS Collaboration; Karapınar, GülerConstraints are presented on the total width of the recently discovered Higgs boson, ΓH, using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1fb -1 at a center-of-mass energy s=7TeV and 19.7fb -1 at s=8TeV. A simultaneous maximum likelihood fit to the measured kinematic distributions near the resonance peak and above the Z-boson pair production threshold leads to an upper limit on the Higgs boson width of ΓH < 22MeV at a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass of mH = 125.6GeV. © 2014 Elsevier B.V.