Mathematics / Matematik
Permanent URI for this collectionhttps://hdl.handle.net/11147/8
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Article Citation - WoS: 121Citation - Scopus: 185Observation of Electroweak Production of Same-Sign W Boson Pairs in the Two Jet and Two Same-Sign Lepton Final State in Proton-Proton Collisions at S =13 Tev(American Physical Society, 2018) Karapınar, GülerThe first observation of electroweak production of same-sign W boson pairs in proton-proton collisions is reported. The data sample corresponds to an integrated luminosity of 35.9 fb-1 collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. Events are selected by requiring exactly two leptons (electrons or muons) of the same charge, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass. The observed significance of the signal is 5.5 standard deviations, where a significance of 5.7 standard deviations is expected based on the standard model. The ratio of measured event yields to that expected from the standard model at leading order is 0.90±0.22. A cross section measurement in a fiducial region is reported. Bounds are given on the structure of quartic vector boson interactions in the framework of dimension-8 effective field theory operators and on the production of doubly charged Higgs bosons.Article Citation - WoS: 54Citation - Scopus: 93Inclusive Search for a Highly Boosted Higgs Boson Decaying To a Bottom Quark-Antiquark Pair(American Physical Society, 2018) CMS Collaboration; Karapınar, GülerAn inclusive search for the standard model Higgs boson (H) produced with large transverse momentum (pT) and decaying to a bottom quark-antiquark pair (bb) is performed using a data set of pp collisions at s=13 TeV collected with the CMS experiment at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb-1. A highly Lorentz-boosted Higgs boson decaying to bb is reconstructed as a single, large radius jet, and it is identified using jet substructure and dedicated b tagging techniques. The method is validated with Z→bb decays. The Z→bb process is observed for the first time in the single-jet topology with a local significance of 5.1 standard deviations (5.8 expected). For a Higgs boson mass of 125 GeV, an excess of events above the expected background is observed (expected) with a local significance of 1.5 (0.7) standard deviations. The measured cross section times branching fraction for production via gluon fusion of H→bb with reconstructed pT>450 GeV and in the pseudorapidity range -2.5<η<2.5 is 74±48(stat)-10+17(syst) fb, which is consistent within uncertainties with the standard model prediction. © 2018 CERN.Article Citation - WoS: 61Citation - Scopus: 60Measurement of the Top Quark Pair Production Cross Section in Proton-Proton Collisions at S =13 Tev(American Physical Society, 2016) CMS Collaboration; Karapınar, GülerThe top quark pair production cross section is measured for the first time in proton-proton collisions at s=13 TeV by the CMS experiment at the CERN LHC, using data corresponding to an integrated luminosity of 43 pb-1. The measurement is performed by analyzing events with at least one electron and one muon of opposite charge, and at least two jets. The measured cross section is 746±58(stat)±53(syst)±36(lumi) pb, in agreement with the expectation from the standard model.Article Citation - WoS: 9Citation - Scopus: 78Reconstruction and Identification of ? Lepton Decays To Hadrons and ?? at Cms(IOP Publishing Ltd., 2016) CMS Collaboration; Karapınar, GülerThis paper describes the algorithms used by the CMS experiment to reconstruct and identify τ → hadrons + νtau; decays during Run 1 of the LHC. The performance of the algorithms is studied in proton-proton collisions recorded at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb-1. The algorithms achieve an identification efficiency of 50-60%, with misidentification rates for quark and gluon jets, electrons, and muons between per mille and per cent levels.Article Citation - WoS: 158Citation - Scopus: 381Observation of the Rare B0s??+?- Decay From the Combined Analysis of Cms and Lhcb Data(Nature Publishing Group, 2015) CMS Collaboration; Karapınar, GülerThe standard model of particle physics describes the fundamental particles and their interactions via the strong, electromagnetic and weak forces. It provides precise predictions for measurable quantities that can be tested experimentally. The probabilities, or branching fractions, of the strangeB meson (B0 s ) andtheB0meson decaying into two oppositely charged muons (μ+ and μ-) are especially interesting because of their sensitivity to theories that extend the standard model. The standard model predicts that the B0s→μ+μ- and B0s→μ+μ- decays are very rare, with about four of the former occurring for every billion B0 s mesons produced, and one of the latter occurring for every ten billion B0 mesons1. A difference in the observed branching fractions with respect to the predictions of the standard model would provide a direction in which the standard model should be extended. Before the Large Hadron Collider (LHC) at CERN2 started operating, no evidence for either decay mode had been found. Upper limits on the branching fractions were an order of magnitude above the standard model predictions. The CMS (CompactMuonSolenoid) andLHCb(LargeHadronCollider beauty) collaborations have performed a joint analysis of the data from proton'proton collisions that they collected in 2011 at a centre-ofmass energy of seven teraelectronvolts and in 2012 at eight teraelectronvolts. Here we report the first observation of the B0s→μ+μ- decay, with a statistical significance exceeding six standard deviations, and the best measurement so far of its branching fraction. Furthermore, we obtained evidence for the B0s→μ+μ- decay with a statistical significance of three standard deviations. Both measurements are statistically compatible with standard model predictions and allow stringent constraints to be placed on theories beyond the standardmodel. The LHCexperimentswill resume taking data in 2015, recording proton'proton collisions at a centre-of-mass energy of 13 teraelectronvolts, which will approximately double the production rates of B0s and B0 mesons and lead to further improvements in the precision of these crucial tests of the standard model. © 2015 Macmillan Publishers Limited. All rights reserved.Article Citation - WoS: 453Citation - Scopus: 360Identification of B-Quark Jets With the Cms Experiment(IOP Publishing Ltd., 2013) CMS Collaboration; Karapınar, GülerAt the Large Hadron Collider, the identification of jets originating from b quarks is important for searches for new physics and for measurements of standard model processes. A variety of algorithms has been developed by CMS to select b-quark jets based on variables such as the impact parameters of charged-particle tracks, the properties of reconstructed decay vertices, and the presence or absence of a lepton, or combinations thereof. The performance of these algorithms has been measured using data from proton-proton collisions at the LHC and compared with expectations based on simulation. The data used in this study were recorded in 2011 at s = 7 TeV for a total integrated luminosity of 5.0 fb-1. The efficiency for tagging b-quark jets has been measured in events from multijet and t-quark pair production. CMS has achieved a b-jet tagging efficiency of 85% for a light-parton misidentification probability of 10% in multijet events. For analyses requiring higher purity, a misidentification probability of only 1.5% has been achieved, for a 70% b-jet tagging efficiency. © 2013 IOP Publishing Ltd and Sissa Medialab srl.