Rectorate / Rektörlük
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Article Citation - WoS: 21Citation - Scopus: 25Search for a Heavy Vector Resonance Decaying To a Z Boson and a Higgs Boson in Proton-Proton Collisions at <mml:msqrt>s</Mml:msqrt>=13 Te(Springer, 2021) CMS Collaboration; Karapınar, GülerA search is presented for a heavy vector resonance decaying into a Z boson and the standard model Higgs boson, where the Z boson is identified through its leptonic decays to electrons, muons, or neutrinos, and the Higgs boson is identified through its hadronic decays. The search is performed in a Lorentz-boosted regime and is based on data collected from 2016 to 2018 at the CERN LHC, corresponding to an integrated luminosity of 137 fb-1. Upper limits are derived on the production of a narrow heavy resonance Z ', and a mass below 3.5 and 3.7 Te is excluded at 95% confidence level in models where the heavy vector boson couples predominantly to fermions and to bosons, respectively. These are the most stringent limits placed on the Heavy Vector Triplet Z ' model to date. If the heavy vector boson couples exclusively to standard model bosons, upper limits on the product of the cross section and branching fraction are set between 23 and 0.3 fb for a Z ' mass between 0.8 and 4.6 Te, respectively. This is the first limit set on a heavy vector boson coupling exclusively to standard model bosons in its production and decay.Article Citation - WoS: 60Citation - Scopus: 81Measurements of Production Cross Sections of the Higgs Boson in the Four-Lepton Final State in Proton-Proton Collisions at Root S=13 Tev(Springer, 2021) Karapınar, Güler; CMS CollaborationProduction cross sections of the Higgs boson are measured in the H -> ZZ -> 4l (l = e, mu) decay channel. A data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS detector at the LHC and corresponding to an integrated luminosity of 137 fb(-1) is used. The signal strength modifier mu, defined as the ratio of the Higgs boson production rate in the 4l channel to the standard model (SM) expectation, is measured to be mu = 0.94 +/- 0.07 (stat)(-0.08)(+0.09) (syst) at a fixed value of m(H) = 125.38 GeV. The signal strength modifiers for the individual Higgs boson production modes are also reported. The inclusive fiducial cross section for the H -> 4l process is measured to be 2.84(-0.22)(+0.23) (stat)(-0.21)(+0.26) (syst) fb, which is compatible with the SM prediction of 2.84 +/- 0.15 fb for the same fiducial region. Differential cross sections as a function of the transverse momentum and rapidity of the Higgs boson, the number of associated jets, and the transverse momentum of the leading associated jet are measured. A new set of cross section measurements in mutually exclusive categories targeted to identify production mechanisms and kinematical features of the events is presented. The results are in agreement with the SM predictions.Article Citation - WoS: 35Citation - Scopus: 42Search for Charged Higgs Bosons Produced in Vector Boson Fusion Processes and Decaying Into Vector Boson Pairs in Proton-Proton Collisions at Root S=13 Tev(Springer, 2021) CMS Collaboration; Karapınar, GülerA search for charged Higgs bosons produced in vector boson fusion processes and decaying into vector bosons, using proton-proton collisions at root s = 13 TeV at the LHC, is reported. The data sample corresponds to an integrated luminosity of 137 fb(-1) collected with the CMS detector. Events are selected by requiring two or three electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass. No excess of events with respect to the standard model background predictions is observed. Model independent upper limits at 95% confidence level are reported on the product of the cross section and branching fraction for vector boson fusion production of charged Higgs bosons as a function of mass, from 200 to 3000 GeV. The results are interpreted in the context of the Georgi-Machacek model.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: 33Citation - Scopus: 75Search for an Exotic Decay of the Higgs Boson To a Pair of Light Pseudoscalars in the Final State With Two B Quarks and Two Τ Leptons in Proton–proton Collisions at S=13tev(Elsevier B.V., 2018) Sirunyan,A.M.; Tumasyan,A.; Adam,W.; Ambrogi,F.; Asilar,E.; Bergauer,T.; Adzic,P.A search for an exotic decay of the Higgs boson to a pair of light pseudoscalar bosons is performed for the first time in the final state with two b quarks and two τ leptons. The search is motivated in the context of models of physics beyond the standard model (SM), such as two Higgs doublet models extended with a complex scalar singlet (2HDM + S), which include the next-to-minimal supersymmetric SM (NMSSM). The results are based on a data set of proton–proton collisions corresponding to an integrated luminosity of 35.9fb−1, accumulated by the CMS experiment at the LHC in 2016 at a center-of-mass energy of 13TeV. Masses of the pseudoscalar boson between 15 and 60GeV are probed, and no excess of events above the SM expectation is observed. Upper limits between 3 and 12% are set on the branching fraction B(h→aa→2τ2b) assuming the SM production of the Higgs boson. Upper limits are also set on the branching fraction of the Higgs boson to two light pseudoscalar bosons in different 2HDM + S scenarios. Assuming the SM production cross section for the Higgs boson, the upper limit on this quantity is as low as 20% for a mass of the pseudoscalar of 40GeV in the NMSSM. © 2018 The Author(s)Article Citation - WoS: 187Citation - Scopus: 313Observation of Higgs Boson Decay To Bottom Quarks(American Physical Society, 2018) CMS Collaboration; Karapınar, GülerThe observation of the standard model (SM) Higgs boson decay to a pair of bottom quarks is presented. The main contribution to this result is from processes in which Higgs bosons are produced in association with a W or Z boson (VH), and are searched for in final states including 0, 1, or 2 charged leptons and two identified bottom quark jets. The results from the measurement of these processes in a data sample recorded by the CMS experiment in 2017, comprising 41.3 fb-1 of proton-proton collisions at s=13 TeV, are described. When combined with previous VH measurements using data collected at s=7, 8, and 13 TeV, an excess of events is observed at mH=125 GeV with a significance of 4.8 standard deviations, where the expectation for the SM Higgs boson is 4.9. The corresponding measured signal strength is 1.01±0.22. The combination of this result with searches by the CMS experiment for H→bb in other production processes yields an observed (expected) significance of 5.6 (5.5) standard deviations and a signal strength of 1.04±0.20.Article Citation - WoS: 102Citation - Scopus: 153Search for Additional Neutral Mssm Higgs Bosons in the ? ? Final State in Proton-Proton Collisions at ?s=13 Tev(Springer Verlag, 2018) CMS Collaboration; Karapınar, GülerA search is presented for additional neutral Higgs bosons in the τ τ final state in proton-proton collisions at the LHC. The search is performed in the context of the minimal supersymmetric extension of the standard model (MSSM), using the data collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes production of the Higgs boson in association with b quarks. No significant deviation above the expected background is observed. Model-independent limits at 95% confidence level (CL) are set on the product of the branching fraction for the decay into τ leptons and the cross section for the production via gluon fusion or in association with b quarks. These limits range from 18 pb at 90 GeV to 3.5 fb at 3.2 TeV for gluon fusion and from 15 pb (at 90 GeV) to 2.5 fb (at 3.2 TeV) for production in association with b quarks, assuming a narrow width resonance. In the mh hod + scenario these limits translate into a 95% CL exclusion of tan β > 6 for neutral Higgs boson masses below 250 GeV, where tan β is the ratio of the vacuum expectation values of the neutral components of the two Higgs doublets. The 95% CL exclusion contour reaches 1.6 TeV for tan β = 60.Article Citation - WoS: 10Citation - Scopus: 33Search for Dark Matter Produced in Association With a Higgs Boson Decaying To ?? or ? + ? - at ?s=13 Tev(Springer Verlag, 2018) CMS Collaboration; Karapınar, GülerA search for dark matter particles is performed by looking for events with large transverse momentum imbalance and a recoiling Higgs boson decaying to either a pair of photons or a pair of τ leptons. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV collected at the CERN LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb−1. No significant excess over the expected standard model background is observed. Upper limits at 95% confidence level are presented for the product of the production cross section and branching fraction in the context of two benchmark simplified models. For the Z′-two-Higgs-doublet model (where Z′ is a new massive boson mediator) with an intermediate heavy pseudoscalar particle of mass mA = 300 GeV and mDM = 100 GeV, the Z′ masses from 550 GeV to 1265 GeV are excluded. For a baryonic Z′ model, with mDM = 1 GeV, Z′ masses up to 615 GeV are excluded. Results are also presented for the spin-independent cross section for the dark matter-nucleon interaction as a function of the mass of the dark matter particle. This is the first search for dark matter particles produced in association with a Higgs boson decaying to two τ leptons