Rectorate / Rektörlük
Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
Browse
15 results
Search Results
Article Citation - WoS: 13Citation - Scopus: 26Search for Chargino-Neutralino Production in Events With Higgs and W Bosons Using 137 Fb(-1) of Proton-Proton Collisions at Root S=13 Tev(Springer, 2021) Karapınar, Güler; CMS CollaborationA search for electroweak production of supersymmetric (SUSY) particles in final states with one lepton, a Higgs boson decaying to a pair of bottom quarks, and large missing transverse momentum is presented. The search uses data from proton-proton collisions at a center-of-mass energy of 13 TeV collected using the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb(-1). The observed yields are consistent with backgrounds expected from the standard model. The results are interpreted in the context of a simplified SUSY model of chargino-neutralino production, with the chargino decaying to a W boson and the lightest SUSY particle (LSP) and the neutralino decaying to a Higgs boson and the LSP. Charginos and neutralinos with masses up to 820 GeV are excluded at 95% confidence level when the LSP mass is small, and LSPs with mass up to 350 GeV are excluded when the masses of the chargino and neutralino are approximately 700 GeV.Article Citation - WoS: 8Citation - Scopus: 49Measurement of the Inclusive and Differential Higgs Boson Production Cross Sections in the Leptonic Ww Decay Mode at P Root S=13 Tev(Springer, 2021) CMS Collaboration; Karapınar, GülerMeasurements of the fiducial inclusive and differential production cross sections of the Higgs boson in proton-proton collisions at root s = 13 TeV are performed using events where the Higgs boson decays into a pair of W bosons that subsequently decay into a final state with an electron, a muon, and a pair of neutrinos. The analysis is based on data collected with the CMS detector at the LHC during 2016-2018, corresponding to an integrated luminosity of 137 fb(-1). Production cross sections are measured as a function of the transverse momentum of the Higgs boson and the associated jet multiplicity. The Higgs boson signal is extracted and simultaneously unfolded to correct for selection efficiency and resolution effects using maximum-likelihood fits to the observed distributions in data. The integrated fiducial cross section is measured to be 86.5 +/- 9.5 fb, consistent with the Standard Model expectation of 82.5 +/- 4.2 fb. No significant deviation from the Standard Model expectations is observed in the differential measurements.Article Citation - WoS: 44Citation - Scopus: 78Search for Nonresonant Higgs Boson Pair Production in Final States With Two Bottom Quarks and Two Photons in Proton-Proton Collisions at Root S=13 Tev(Springer, 2021) CMS Collaboration; Karapınar, GülerA search for nonresonant production of Higgs boson pairs via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two photons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of root s = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb(-1). No significant deviation from the background-only hypothesis is observed. An upper limit at 95% confidence level is set on the product of the Higgs boson pair production cross section and branching fraction into gamma gamma b (b) over bar. The observed (expected) upper limit is determined to be 0.67 (0.45) fb, which corresponds to 7.7 (5.2) times the standard model prediction. This search has the highest sensitivity to Higgs boson pair production to date. Assuming all other Higgs boson couplings are equal to their values in the standard model, the observed coupling modifiers of the trilinear Higgs boson self-coupling kappa(lambda) and the coupling between a pair of Higgs bosons and a pair of vector bosons c(2V) are constrained within the ranges -3.3 < kappa(lambda) < 8.5 and -1.3 < c(2V) < 3.5 at 95% confidence level. Constraints on kappa(lambda) are also set by combining this analysis with a search for single Higgs bosons decaying to two photons, produced in association with top quark-antiquark pairs, and by performing a simultaneous fit of kappa(lambda) and the top quark Yukawa coupling modifier kappa(t).Article Citation - WoS: 104Citation - Scopus: 119Measurements of Higgs Boson Production Cross Sections and Couplings in the Diphoton Decay Channel at Root S=13 Tev(Springer, 2021) Karapınar, Güler; CMS CollaborationMeasurements of Higgs boson production cross sections and couplings in events where the Higgs boson decays into a pair of photons are reported. Events are selected from a sample of proton-proton collisions at root s = 13TeV collected by the CMS detector at the LHC from 2016 to 2018, corresponding to an integrated luminosity of 137 fb(-1). Analysis categories enriched in Higgs boson events produced via gluon fusion, vector boson fusion, vector boson associated production, and production associated with top quarks are constructed. The total Higgs boson signal strength, relative to the standard model (SM) prediction, is measured to be 1.12 +/- 0.09. Other properties of the Higgs boson are measured, including SM signal strength modifiers, production cross sections, and its couplings to other particles. These include the most precise measurements of gluon fusion and vector boson fusion Higgs boson production in several different kinematic regions, the first measurement of Higgs boson production in association with a top quark pair in five regions of the Higgs boson transverse momentum, and an upper limit on the rate of Higgs boson production in association with a single top quark. All results are found to be in agreement with the SM expectations.Article Citation - WoS: 74Citation - Scopus: 73Search for Charged Higgs Bosons Decaying Into a Top and a Bottom Quark in the All-Jet Final State of Pp Collisions at Root S=13 Tev(Springer Verlag, 2020) CMS Collaboration; Karapınar, GülerA search for charged Higgs bosons (H-+/-) decaying into a top and a bottom quark in the all-jet final state is presented. The analysis uses LHC proton-proton collision data recorded with the CMS detector in 2016 at root s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). No significant excess is observed above the expected background. Model-independent upper limits at 95% confidence level are set on the product of the H-+/- production cross section and branching fraction in two scenarios. For production in association with a top quark, limits of 21.3 to 0.007 pb are obtained for H-+/- masses in the range of 0.2 to 3 TeV. Combining this with a search in leptonic final states results in improved limits of 9.25 to 0.005 pb. The complementary s-channel production of an H-+/- is investigated in the mass range of 0.8 to 3 TeV and the corresponding upper limits are 4.5 to 0.023 pb. These results are interpreted using different minimal supersymmetric extensions of the standard model.Article Citation - WoS: 26Citation - Scopus: 46Search for a Light Pseudoscalar Higgs Boson in the Boosted Mu Mu Tau Tau Final State in Proton-Proton Collisions at Root S=13 Tev(Springer Verlag, 2020) Karapınar, GülerA search for a light pseudoscalar Higgs boson (a) decaying from the 125 GeV (or a heavier) scalar Higgs boson (H) is performed using the 2016 LHC proton-proton collision data at root s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1), collected by the CMS experiment. The analysis considers gluon fusion and vector boson fusion production of the H, followed by the decay H -> aa -> mu mu tau tau, and considers pseudoscalar masses in the range 3.6 < m(a) < 21 GeV. Because of the large mass difference between the H and the a bosons and the small masses of the a boson decay products, both the mu mu and the tau tau pairs have high Lorentz boost and are collimated. The tau tau reconstruction efficiency is increased by modifying the standard technique for hadronic tau lepton decay reconstruction to account for a nearby muon. No significant signal is observed. Model-independent limits are set at 95% confidence level, as a function of m(a), on the branching fraction (B) for H -> aa -> mu mu tau tau, down to 1.5 (2.0)x10(-4) for m(H) = 125 (300) GeV. Model-dependent limits on B(H -> aa) are set within the context of two Higgs doublets plus singlet models, with the most stringent results obtained for Type-III models. These results extend current LHC searches for heavier a bosons that decay to resolved lepton pairs and provide the first such bounds for an H boson with a mass above 125 GeV.Article Citation - WoS: 4Citation - Scopus: 8Search for Decays of the 125 Gev Higgs Boson Into a Z Boson and a Rho or Phi Meson(Springer Verlag, 2020) CMS Collaboration; Karapınar, GülerDecays of the 125 GeV Higgs boson into a Z boson and a rho (0)(770) or (1020) meson are searched for using proton-proton collision data collected by the CMS experiment at the LHC at <mml:msqrt>s</mml:msqrt> = 13 TeV. The analysed data set corresponds to an integrated luminosity of 137 fb(-1). Events are selected in which the Z boson decays into a pair of electrons or a pair of muons, and the rho and phi mesons decay into pairs of pions and kaons, respectively. No significant excess above the background model is observed. As different polarization states are possible for the decay products of the Z boson and rho or phi mesons, affecting the signal acceptance, scenarios in which the decays are longitudinally or transversely polarized are considered. Upper limits at the 95% confidence level on the Higgs boson branching fractions into Z rho and Z phi are determined to be 1.04-1.31% and 0.31-0.40%, respectively, where the ranges reflect the considered polarization scenarios; these values are 740-940 and 730-950 times larger than the respective standard model expectations. These results constitute the first experimental limits on the two decay channels.Article Citation - WoS: 41Citation - Scopus: 50Inclusive Search for Highly Boosted Higgs Bosons Decaying To Bottom Quark-Antiquark Pairs in Proton-Proton Collisions at ?s = 13 Tev(Springer Verlag, 2020) CMS Collaboration; Karapınar, GülerA search for standard model Higgs bosons (H) produced with transverse momentum (pT) greater than 450 GeV and decaying to bottom quark-antiquark pairs (b b ¯) is performed using proton-proton collision data collected by the CMS experiment at the LHC at s = 13 TeV. The data sample corresponds to an integrated luminosity of 137 fb?1. The search is inclusive in the Higgs boson production mode. Highly Lorentz-boosted Higgs bosons decaying to b b ¯ are reconstructed as single large-radius jets, and are identified using jet substructure and a dedicated b tagging technique based on a deep neural network. The method is validated with Z ?b b ¯ decays. For a Higgs boson mass of 125 GeV, an excess of events above the background assuming no Higgs boson production is observed with a local significance of 2.5 standard deviations (?), while the expectation is 0.7. The corresponding signal strength and local significance with respect to the standard model expectation are ?H = 3.7 ± 1.2(stat)?0.7+0.8(syst)?0.5+0.8(theo) and 1.9 ?. Additionally, an unfolded differential cross section as a function of Higgs boson pT for the gluon fusion production mode is presented, assuming the other production modes occur at the expected rates. [Figure not available: see fulltext.] © 2020, The Author(s).Article Citation - WoS: 50Citation - Scopus: 57Search for a Charged Higgs Boson Decaying Into Top and Bottom Quarks in Events With Electrons or Muons in Proton-Proton Collisions at Root S=13tev(Springer Verlag, 2020) Karapınar, Güler; CMS CollaborationA search is presented for a charged Higgs boson heavier than the top quark, produced in association with a top quark, or with a top and a bottom quark, and decaying into a top-bottom quark-antiquark pair. The search is performed using proton-proton collision data collected by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). Events are selected by the presence of a single isolated charged lepton (electron or muon) or an opposite-sign dilepton (electron or muon) pair, categorized according to the jet multiplicity and the number of jets identified as originating from b quarks. Multivariate analysis techniques are used to enhance the discrimination between signal and background in each category. The data are compatible with the standard model, and 95% confidence level upper limits of 9.6-0.01 pb are set on the charged Higgs boson production cross section times branching fraction to a top-bottom quark-antiquark pair, for charged Higgs boson mass hypotheses ranging from 200 GeV to 3 TeV. The upper limits are interpreted in different minimal supersymmetric extensions of the standard model.Article Citation - WoS: 3Citation - Scopus: 50Search for New Neutral Higgs Bosons Through the H -> Za -><mml:msup>l+</Mml:msup><mml:msup>l-< Stretchy="true"><overbar></Mml:mover> Process in Pp Collisions at <mml:msqrt>s</Mml:msqrt>=13 Tev(Springer Verlag, 2020) Karapınar, Güler; CMS CollaborationThis paper reports on a search for an extension to the scalar sector of the standard model, where a new CP-even (odd) boson decays to a Z boson and a lighter CP-odd (even) boson, and the latter further decays to a b quark pair. The Z boson is reconstructed via its decays to electron or muon pairs. The analysed data were recorded in proton-proton collisions at a center-of-mass energy <mml:msqrt>s</mml:msqrt> = 13 TeV, collected by the CMS experiment at the LHC during 2016, corresponding to an integrated luminosity of 35.9 fb(-1). Data and predictions from the standard model are in agreement within the uncertainties. Upper limits at 95% confidence level are set on the production cross section times branching fraction, with masses of the new bosons up to 1000 GeV. The results are interpreted in the context of the two-Higgs-doublet model.