Rectorate / Rektörlük
Permanent URI for this collectionhttps://hdl.handle.net/11147/6849
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Article Citation - WoS: 73Measurement of the Polarization of W Bosons With Large Transverse Momenta in W Plus Jets Events at the Lhc(American Physical Society, 2011) Karapınar, GülerA first measurement of the polarization of W bosons with large transverse momenta in pp collisions is presented. The measurement is based on 36 pb(-1) of data recorded at root s = 7 TeV by the CMS detector at the LHC. The left-handed, right-handed, and longitudinal polarization fractions (f(L), f(R), and f(0), respectively) of W bosons with transverse momenta larger than 50 GeV are determined by using decays to both electrons and muons. The muon final state yields the most precise measurement: (f(L) - f(R))(-) = 0.240 +/- 0.036(syst) +/- 0.031(syst) and f(0)(-) = 0.183 +/- 0.087(stat) +/- 0.123(syst) for negatively charged W bosons and (f(L) - f(R))(+) = 0.310 +/- 0.036(syst) +/- 0.017(syst) and f(0)(+) = 0.171 +/- 0.085(syst) +/- 0.099(syst) for positively charged W bosons. This establishes, for the first time, that W bosons produced in pp collisions with large transverse momenta are predominantly left-handed, as expected in the standard model.Article Citation - WoS: 47Search for Heavy Neutrinos and W-R Bosons With Right-Handed Couplings in a Left-Right Symmetric Model in Pp Collisions at Root S=7 Tev(American Physical Society, 2012) Karapınar, GülerResults are presented from a search for heavy, right-handed muon neutrinos, N-mu, and right-handed W-R bosons, which arise in the left-right symmetric extensions of the standard model. The analysis is based on a 5: 0 fb(-1) sample of proton-proton collisions at a center-of-mass energy of 7 TeV, collected by the CMS detector at the Large Hadron Collider. No evidence is observed for an excess of events over the standard model expectation. For models with exact left-right symmetry, heavy right-handed neutrinos are excluded at 95% confidence level for a range of neutrino masses below the WR mass, dependent on the value of M-WR. The excluded region in the two-dimensional (M-WR, MN mu) mass plane extends to M-WR = 2.5TeV. DOI: 10.1103/PhysRevLett.109.261802Article Citation - WoS: 20Measurement of the Azimuthal Anisotropy of Neutral Pions in Pb-Pb Collisions at Root S-Nn=2.76 Tev(American Physical Society, 2013) Karapınar, GülerFirst measurements of the azimuthal anisotropy of neutral pions produced in Pb-Pb collisions at a center-of-mass energy of root S-NN = 2.76 TeV are presented. The amplitudes of the second Fourier component (upsilon(2)) of the pi(0) azimuthal distributions are extracted using an event-plane technique. The values of upsilon(2) are studied as a function of the neutral pion transverse momentum (p(T)) for different classes of collision centrality in the kinematic range 1.6< p(T)<8.0 GeV/c, within the pseudorapidity interval vertical bar eta vertical bar < 0.8. The CMS measurements of upsilon(2)(p(T)) are similar to previously reported pi(0) azimuthal anisotropy results from root S-NN = 200 GeV Au-Au collisions at RHIC, despite a factor of similar to 14 increase in the centerof-mass energy. In the momentum range 2.5<p(T)<5.0 GeV/c, the neutral pion anisotropies are found to be smaller than those observed by CMS for inclusive charged particles. DOI: 10.1103/PhysRevLett.110.042301Article Citation - WoS: 131Evidence for Associated Production of a Single Top Quark and W Boson in Pp Collisions at Root S=7 Tev(American Physical Society, 2013) Karapınar, GülerEvidence is presented for the associated production of a single top quark and W boson in pp collisions at root s = 7 TeV with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 4.9 fb(-1). The measurement is performed using events with two leptons and a jet originated from a b quark. A multivariate analysis based on kinematic properties is utilized to separate the t (t) over bar background from the signal. The observed signal has a significance of 4.0 sigma and corresponds to a cross section of 16(-4)(+5) pb, in agreement with the standard model expectation of 15.6 +/- 0.4(-1.2)(+1.0) pb. DOI: 10.1103/PhysRevLett.110.022003Article Citation - WoS: 21Observation of a Diffractive Contribution To Dijet Production in Proton-Proton Collisions at Root S = 7 Tev(American Physical Society, 2013) Karapınar, GülerThe cross section for dijet production in proton-proton collisions at root s = 7 TeV is presented as a function of (xi) over tilde, a variable that approximates the fractional momentum loss of the scattered proton in single-diffractive events. The analysis is based on an integrated luminosity of 2.7 nb(-1) collected with the CMS detector at the LHC at low instantaneous luminosities, and uses events with jet transverse momentum of at least 20 GeV. The dijet cross section results are compared to the predictions of diffractive and non-diffractive models. The low-(xi) over tilde data show a significant contribution from diffractive dijet production, observed for the first time at the LHC. The associated rapidity gap survival probability is estimated. DOI: 10.1103/PhysRevD.87.012006Article Citation - WoS: 4Search for Contact Interactions in Mu(+)mu(-) Events in Pp Collisions at Root S = 7 Tev(American Physical Society, 2013) Karapınar, GülerResults are reported from a search for the effects of contact interactions using events with a high-mass, oppositely charged muon pair. The events are collected in proton-proton collisions at root s = 7 TeV using the Compact Muon Solenoid detector at the Large Hadron Collider. The data sample corresponds to an integrated luminosity of 5: 3 fb(-1). The observed dimuon mass spectrum is consistent with that expected from the standard model. The data are interpreted in the context of a quark-and muon-compositeness model with a left-handed isoscalar current and an energy scale parameter Lambda. The 95% confidence level lower limit on Lambda is 9.5 TeV under the assumption of destructive interference between the standard model and contact-interaction amplitudes. For constructive interference, the limit is 13.1 TeV. These limits are comparable to the most stringent ones reported to date. DOI: 10.1103/PhysRevD.87.032001Article Citation - WoS: 48Measurement of the Upsilon(1s), Upsilon(2s), and Upsilon(3s) Polarizations in Pp Collisions at Root S 7 Tev(American Physical Society, 2013) Karapınar, GülerThe polarizations of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) mesons are measured in proton-proton collisions at root s = 7 TeV, using a data sample of Upsilon(nS) -> mu(+)mu(-) decays collected by the CMS experiment, corresponding to an integrated luminosity of 4.9 fb(-1). The dimuon decay angular distributions are analyzed in three different polarization frames. The polarization parameters lambda(theta), lambda(phi), and lambda(theta phi), as well as the frame-invariant quantity (lambda) over tilde, are presented as a function of the Upsilon(nS) transverse momentum between 10 and 50 GeV, in the rapidity ranges vertical bar y vertical bar < 0: 6 and 0: 6 < vertical bar y vertical bar < 1.2. No evidence of large transverse or longitudinal polarizations is seen in the explored kinematic region. DOI: 10.1103/PhysRevLett.110.081802Article Citation - WoS: 47Search for Pair Production of Third-Generation Leptoquarks and Top Squarks in Pp Collisions at Root S=7 Tev(American Physical Society, 2013) Karapınar, GülerResults are presented from a search for the pair production of third-generation scalar and vector leptoquarks, as well as for top squarks in R-parity-violating supersymmetric models. In either scenario, the new, heavy particle decays into a tau lepton and a b quark. The search is based on a data sample of pp collisions at root s = 7 TeV, which is collected by the CMS detector at the LHC and corresponds to an integrated luminosity of 4.8 fb(-1). The number of observed events is found to be in agreement with the standard model prediction, and exclusion limits on mass parameters are obtained at the 95% confidence level. Vector leptoquarks with masses below 760 GeV are excluded and, if the branching fraction of the scalar leptoquark decay to a tau lepton and a b quark is assumed to be unity, third-generation scalar leptoquarks with masses below 525 GeV are ruled out. Top squarks with masses below 453 GeV are excluded for a typical benchmark scenario, and limits on the coupling between the top squark, tau lepton, and b quark, lambda'(333) are obtained. These results are the most stringent for these scenarios to date. DOI: 10.1103/PhysRevLett.110.081801Article Citation - WoS: 10Search for Supersymmetry in Final States With a Single Lepton, B-Quark Jets, and Missing Transverse Energy in Proton-Proton Collisions at Root S=7 Tev(American Physical Society, 2013) Karapınar, GülerA search motivated by supersymmetric models with light top squarks is presented using proton-proton collision data recorded with the CMS detector at a center-of-mass energy of root s = 7 TeV during 2011, corresponding to an integrated luminosity of 4.98 fb(-1). The analysis is based on final states with a single lepton, b-quark jets, and missing transverse energy. Standard model yields are predicted from data using two different approaches. The observed event numbers are found to be compatible with these predictions. Results are interpreted in the context of the constrained minimal supersymmetric standard model and of a simplified model with four top quarks in the final state. DOI: 10.1103/PhysRevD.87.052006Article Citation - WoS: 303Study of the Mass and Spin-Parity of the Higgs Boson Candidate Via Its Decays To Z Boson Pairs(American Physical Society, 2013) Karapınar, GülerA study is presented of the mass and spin-parity of the new boson recently observed at the LHC at a mass near 125 GeV. An integrated luminosity of 17: 3 fb(-1), collected by the CMS experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, is used. The measured mass in the ZZ channel, where both Z bosons decay to e or mu pairs, is 126: 2 +/- 0.6(stat) +/- 0. 2(syst) GeV. The angular distributions of the lepton pairs in this channel are sensitive to the spin-parity of the boson. Under the assumption of spin 0, the present data are consistent with the pure scalar hypothesis, while disfavoring the pure pseudoscalar hypothesis. DOI: 10.1103/PhysRevLett.110.081803