Mathematics / Matematik
Permanent URI for this collectionhttps://hdl.handle.net/11147/8
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Article Citation - WoS: 17Citation - Scopus: 23Search for R-Parity Violating Supersymmetry in Pp Collisions at S=13tev Using B Jets in a Final State With a Single Lepton, Many Jets, and High Sum of Large-Radius Jet Masses(Elsevier Ltd., 2018) CMS Collaboration; Karapınar, GülerResults are reported from a search for physics beyond the standard model in proton–proton collisions at a center-of-mass energy of s=13TeV. The search uses a signature of a single lepton, large jet and bottom quark jet multiplicities, and high sum of large-radius jet masses, without any requirement on the missing transverse momentum in an event. The data sample corresponds to an integrated luminosity of 35.9 fb−1 recorded by the CMS experiment at the LHC. No significant excess beyond the prediction from standard model processes is observed. The results are interpreted in terms of upper limits on the production cross section for R-parity violating supersymmetric extensions of the standard model using a benchmark model of gluino pair production, in which each gluino decays promptly via g˜→tbs. Gluinos with a mass below 1610 GeV are excluded at 95% confidence level.Article Citation - WoS: 63Citation - Scopus: 76Search for Single Production of a Vector-Like T Quark Decaying To a Z Boson and a Top Quark in Proton–proton Collisions at S=13tev(Elsevier, 2018) CMS Collaboration; Karapınar, GülerA search is presented for single production of a vector-like quark (T) decaying to a Z boson and a top quark, with the Z boson decaying leptonically and the top quark decaying hadronically. The search uses data collected by the CMS experiment in proton–proton collisions at a center-of-mass energy of 13 TeV in 2016, corresponding to an integrated luminosity of 35.9fb−1. The presence of forward jets is a particular characteristic of single production of vector-like quarks that is used in the analysis. For the first time, different T quark width hypotheses are studied, from negligibly small to 30% of the new particle mass. At the 95% confidence level, the product of cross section and branching fraction is excluded above values in the range 0.26–0.04 pb for T quark masses in the range 0.7–1.7 TeV, assuming a negligible width. A similar sensitivity is observed for widths of up to 30% of the T quark mass. The production of a heavy Z′ boson decaying to Tt, with T→tZ, is also searched for, and limits on the product of cross section and branching fractions for this process are set between 0.13 and 0.06 pb for Z′ boson masses in the range from 1.5 to 2.5 TeV.Article Citation - WoS: 36Citation - Scopus: 40Search for New Long-Lived Particles at S=13 Tev(Elsevier Ltd., 2018) CMS Collaboration; Karapınar, GülerA search for long-lived particles was performed with data corresponding to an integrated luminosity of 2.6 fb−1 collected at a center-of-mass energy of 13 TeV by the CMS experiment in 2015. The analysis exploits two customized topological trigger algorithms, and uses the multiplicity of displaced jets to search for the presence of a signal decay occurring at distances between 1 and 1000 mm. The results can be interpreted in a variety of different models. For pair-produced long-lived particles decaying to two b quarks and two leptons with equal decay rates between lepton flavors, cross sections larger than 2.5 fb are excluded for proper decay lengths between 70–100 mm for a long-lived particle mass of 1130 GeV at 95% confidence. For a specific model of pair-produced, long-lived top squarks with R-parity violating decays to a b quark and a lepton, masses below 550–1130 GeV are excluded at 95% confidence for equal branching fractions between lepton flavors, depending on the squark decay length. This mass bound is the most stringent to date for top squark proper decay lengths greater than 3 mm.Article Citation - WoS: 1Citation - Scopus: 1Search for Natural Supersymmetry in Events With Top Quark Pairs and Photons in Pp Collisions at ?s=8 Tev(Springer Verlag, 2018) CMS Collaboration; Karapınar, GülerResults are presented from a search for natural gauge-mediated supersymmetry (SUSY) in a scenario in which the top squark is the lightest squark, the next-to-lightest SUSY particle is a bino-like neutralino, and the lightest SUSY particle is the gravitino. The strong production of top squark pairs can produce events with pairs of top quarks and neutralinos, with each bino-like neutralino decaying to a photon and a gravitino. The search is performed using a sample of pp collision data accumulated by the CMS experiment at s=8 TeV, corresponding to an integrated luminosity of 19.7 fb−1. The final state consists of a lepton (electron or muon), jets, and one or two photons. The imbalance in transverse momentum in the events is compared with the expected spectrum from standard model processes. No excess event yield is observed beyond the expected background, and the result is interpreted in the context of a general model of gauge-mediated SUSY breaking that leads to exclusion of top squark masses below 650–730 GeV.Article Citation - WoS: 29Citation - Scopus: 48Measurement of the Differential Cross Sections for the Associated Production of a W Boson and Jets in Proton-Proton Collisions at Sqrt(s) =13 Tev(American Physical Society, 2017) CMS Collaboration; Karapınar, GülerA measurement of the differential cross sections for a W boson produced in association with jets in the muon decay channel is presented. The measurement is based on 13 TeV proton-proton collision data corresponding to an integrated luminosity of 2.2 fb-1, recorded by the CMS detector at the LHC. The cross sections are reported as functions of jet multiplicity, jet transverse momentum pT, jet rapidity, the scalar pT sum of the jets, and angular correlations between the muon and each jet for different jet multiplicities. The measured cross sections are in agreement with predictions that include multileg leading-order (LO) and next-to-LO matrix element calculations interfaced with parton showers, as well as a next-to-next-to-LO calculation for the W boson and one jet production.Article Citation - WoS: 25Citation - Scopus: 37Measurements of Jet Charge With Dijet Events in Pp Collisions at ?s=8 Tev(Springer Verlag, 2017) CMS Collaboration; Karapınar, GülerJet charge is an estimator of the electric charge of a quark, antiquark, or gluon initiating a jet. It is based on the momentum-weighted sum of the electric charges of the jet constituents. Measurements of three charge observables of the leading jet in transverse momentum pT are performed with dijet events. The analysis is carried out with ata collected by the CMS experiment at the CERN LHC in proton-proton collisions at s=8 TeV corresponding to an integrated luminosity of 19.7fb−1. The results are presented as a function of the pT of the leading jet and compared to predictions from leading- and next-to-leading-order event generators combined with parton showers. Measured jet charge distributions, unfolded for detector effects, are reported, which expand on previous measurements of the jet charge average and standard deviation in pp collisions.Article Citation - WoS: 16Citation - Scopus: 44Search for New Physics in the Monophoton Final State in Proton-Proton Collisions at ?s=13 Tev(Springer Verlag, 2017) CMS Collaboration; Karapınar, GülerA search is conducted for new physics in a final state containing a photon and missing transverse momentum in proton-proton collisions at s=13 TeV. The data collected by the CMS experiment at the CERN LHC correspond to an integrated luminosity of 12.9 fb−1. No deviations are observed relative to the predictions of the standard model. The results are interpreted as exclusion limits on the dark matter production cross sections and parameters in models containing extra spatial dimensions. Improved limits are set with respect to previous searches using the monophoton final state. In particular, the limits on the extra dimension model parameters are the most stringent to date in this channelArticle Citation - WoS: 40Citation - Scopus: 131Coherent J/? Photoproduction in Ultra-Peripheral Pbpb Collisions at Snn=2.76tev With the Cms Experiment(Elsevier Ltd., 2017) CMS Collaboration; Karapınar, GülerThe cross section for coherent J/ψ photoproduction accompanied by at least one neutron on one side of the interaction point and no neutron activity on the other side, Xn0n, is measured with the CMS experiment in ultra-peripheral PbPb collisions at sNN=2.76TeV. The analysis is based on a data sample corresponding to an integrated luminosity of 159μb−1, collected during the 2011 PbPb run. The J/ψ mesons are reconstructed in the dimuon decay channel, while neutrons are detected using zero degree calorimeters. The measured cross section is dσXn0n coh/dy(J/ψ)=0.36±0.04(stat)±0.04(syst) mb in the rapidity interval 1.8<|y|<2.3. Using a model for the relative rate of coherent photoproduction processes, this Xn0n measurement gives a total coherent photoproduction cross section of dσcoh/dy(J/ψ)=1.82±0.22(stat)±0.20(syst)±0.19(theo) mb. The data strongly disfavor the impulse approximation model prediction, indicating that nuclear effects are needed to describe coherent J/ψ photoproduction in γ+Pb interactions. The data are found to be consistent with the leading twist approximation, which includes nuclear gluon shadowing.Other Citation - WoS: 13Citation - Scopus: 9Erratum To: Search for New Physics in Events With Same-Sign Dileptons and Jets in Pp Collisions at ?s=8 Tev(Springer Verlag, 2015) CMS Collaboration; Karapınar, GülerA search for new physics is performed based on events with jets and a pair of isolated, same-sign leptons. The results are obtained using a sample of proton-proton collision data collected by the CMS experiment at a centre-of-mass energy of 8 TeV at the LHC, corresponding to an integrated luminosity of 19.5 fb-1. In order to be sensitive to a wide variety of possible signals beyond the standard model, multiple search regions defined by the missing transverse energy, the hadronic energy, the number of jets and b-quark jets, and the transverse momenta of the leptons in the events are considered. No excess above the standard model background expectation is observed and constraints are set on a number of models for new physics, as well as on the same-sign top-quark pair and quadruple-top-quark production cross sections. Information on event selection efficiencies is also provided, so that the results can be used to confront an even broader class of new physics models.Article Citation - WoS: 42Citation - Scopus: 40Search for a Light Charged Higgs Boson Decaying To Cs¯ in Pp Collisions at ?s=8 Tev(Springer Verlag, 2015) CMS Collaboration; Karapınar, GülerA search for a light charged Higgs boson, originating from the decay of a top quark and subsequently decaying into a charm quark and a strange antiquark, is presented. The data used in the analysis correspond to an integrated luminosity of 19.7 fb−1 recorded in proton-proton collisions at (formula presented.) TeV by the CMS experiment at the LHC. The search is performed in the process tt¯→W±bH∓b¯(formula presented.), where the W boson decays to a lepton (electron or muon) and a neutrino. The decays lead to a final state comprising an isolated lepton, at least four jets and large missing transverse energy. No significant deviation is observed in the data with respect to the standard model predictions, and model-independent upper limits are set on the branching fraction ℬt→(formula presented.), ranging from 1.2 to 6.5% for a charged Higgs boson with mass between 90 and 160 GeV, under the assumption that ℬH+→(formula presented.)[Figure not available: see fulltext.] © 2015, The Author(s).
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