Yazar "Bilki, Burak" seçeneğine göre listele
Listeleniyor 1 - 20 / 394
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Angular Analysis of the Decay B+ ? K?(892)+?+?? in Proton-Proton Collisions at s? = 8 TeV(The CMS Collaboration, 2021) Bilki, Burak; .;, ve diğerAngular distributions of the decay B+-> K*(892)(+)mu(+)mu(-) are studied using events collected with the CMS detector in root s = 8 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 20.0 fb(-1). The forward-backward asymmetry of the muons and the longitudinal polarization of the K*(892)(+) meson are determined as a function of the square of the dimuon invariant mass. These are the first results from this exclusive decay mode and are in agreement with a standard model prediction.Öğe Angular Analysis of the decay B+?K+?+?? in Proton-proton Collisions at ?s=8??TeV(American Physical Society, 2018) Bilki, Burak; ., ve digerThe angular distribution of the flavor-changing neutral current decay B+?K+?+?? is studied in proton-proton collisions at a center-of-mass energy of 8 TeV. The analysis is based on data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 20.5??fb?1. The forward-backward asymmetry AFB of the dimuon system and the contribution FH from the pseudoscalar, scalar, and tensor amplitudes to the decay width are measured as a function of the dimuon mass squared. The measurements are consistent with the standard model expectations.Öğe Azimuthal Correlations For İnclusive 2-Jet, 3-Jet, And 4-Jet Events İn Pp Collisions At S?=13 Tev(The European Physical Journal C, 2018) Bilki, Burak; ., ve digerAzimuthal correlations between the two jets with the largest transverse momenta pTpT in inclusive 2-, 3-, and 4-jet events are presented for several regions of the leading jet pTpT up to 4TeVTeV. For 3- and 4-jet scenarios, measurements of the minimum azimuthal angles between any two of the three or four leading pTpT jets are also presented. The analysis is based on data from proton–proton collisions collected by the CMS Collaboration at a centre-of-mass energy of 13TeVTeV, corresponding to an integrated luminosity of 35.9fb?1fb?1. Calculations based on leading-order matrix elements supplemented with parton showering and hadronization do not fully describe the data, so next-to-leading-order calculations matched with parton shower and hadronization models are needed to better describe the measured distributions. Furthermore, we show that azimuthal jet correlations are sensitive to details of the parton showering, hadronization, and multiparton interactions. A next-to-leading-order calculation matched with parton showers in the MC@NLO method, as implemented in HERWİG 7, gives a better overall description of the measurements than the POWHEG method.Öğe Azimuthal Separation in Nearly Back-To-Back Jet Topologies in İnclusive 2- And 3-Jet Events İn pp Collisions At ?s = 13TeV(The CMS Collaboration, 2019) Bilki, Burak; ., ve diğer.A measurement for inclusive 2- and 3-jet events of the azimuthal correlation between the two jets with the largest transverse momenta, ??12, is presented. The measurement considers events where the two leading jets are nearly collinear (“back-to-back”) in the transverse plane and is performed for several ranges of the leading jet transverse momentum. Proton-proton collision data collected with the CMS experiment at a center-of-mass energy of 13TeV and corresponding to an integrated luminosity of 35.9fb?1 are used. Predictions based on calculations using matrix elements at leading-order and next-to-leading-order accuracy in perturbative quantum chromodynamics supplemented with leading-log parton showers and hadronization are generally in agreement with the measurements. Discrepancies between the measurement and theoretical predictions are as large as 15%, mainly in the region 177?Öğe Beyond nPDFs Effects : Prompt J/? And ?(2s) Production İn pPb And Pp Collisions(The CMS Collaboration, 2019) Bilki, Burak; ., ve diğer.A multi-dimensional analysis of prompt charmonia in pp and pPb collisions at ? sNN = 5.02 TeV with the CMS detector is resented. The pPb differential cross-sections of prompt J/? are shown in a wide kinematic region, for transverse momentum pT spanning from 2 to 30 GeV/c and a rapidity interval between -2.4 to 1.93 in the center of mass of the collision. The final results on prompt ?(2S) meson production cross section in pp and pPb collisions at 5.02 TeV are also reported as a function of pT and rapidity, for pT from 4 to 30 GeV/c. The nuclear modification factor is found to be smaller than that of prompt J/? in all measured bins, especially at low pT and at backward rapidity. Such a different behaviour between the ground and excited states cannot be reproduced considering nPDF effects alone.Öğe Bose-Einstein Correlations İn Pp, Ppb, And Pbpb Collisions At ? Snn = 0.9–7 Tev(American Physical Society, 2018) Bilki, Burak; ., ve digerQuantum-statistical (Bose-Einstein) two-particle correlations are measured in pp collisions at ? s = 0.9, 2.76, and 7 TeV, as well as in pPb and peripheral PbPb collisions at nucleon-nucleon center-of-mass energies of 5.02 and 2.76 TeV, respectively, using the CMS detector at the Large Hadron Collider. Separate analyses are performed for same-sign unidentified charged particles as well as for same-sign pions and kaons identified via their energy loss in the silicon tracker. The characteristics of the one-, two-, and three-dimensional correlation functions are studied as functions of the pair average transverse momentum (kT) and the charged-particle multiplicity in the event. For all systems, the extracted correlation radii steadily increase with the event multiplicity, and decrease with increasing kT. The radii are in the range 1–5 fm, the largest values corresponding to very high multiplicity pPb interactions and to peripheral PbPb collisions with multiplicities similar to those seen in pPb data. It is also observed that the dependencies of the radii on multiplicity and kT largely factorize. At the same multiplicity, the radii are relatively independent of the colliding system and center-of-mass energy.Öğe Bose-Einstein Correlations Of Charged Hadrons İn Proton-Proton Collisions At s=13 TeV(CMS Collaboration, 2020) Bilki, Burak; ., ve diğer.Bose-Einstein correlations of charged hadrons are measured over a broad multiplicity range, from a few particles up to about 250 reconstructed charged hadrons in proton-proton collisions at s = 13 TeV. The results are based on data collected using the CMS detector at the LHC during runs with a special low-pileup configuration. Three analysis techniques with different degrees of dependence on simulations are used to remove the non-Bose-Einstein background from the correlation functions. All three methods give consistent results. The measured lengths of homogeneity are studied as functions of particle multiplicity as well as average pair transverse momentum and mass. The results are compared with data from both CMS and ATLAS at s = 7 TeV, as well as with theoretical predictions.Öğe Calibration Of The Cms Hadron Calorimeters Using Proton-Proton Collision Data At Root s=13 TeV(The CMS Collaboration, 2020) Bilki, Burak; ., ve diğer.Methods are presented for calibrating the hadron calorimeter system of theCMSetector at the LHC. The hadron calorimeters of the CMS experiment are sampling calorimeters of brass and scintillator, and are in the form of one central detector and two endcaps. These calorimeters cover pseudorapidities vertical bar eta vertical bar < 3 and are positioned inside the solenoidal magnet. An outer calorimeter, outside the magnet coil, covers vertical bar eta vertical bar < 1.26, and a steel and quartz-fiber Cherenkov forward calorimeter extends the coverage to vertical bar eta vertical bar < 5.19. The initial calibration of the calorimeters was based on results from test beams, augmented with the use of radioactive sources and lasers. The calibration was improved substantially using proton-proton collision data collected at root s = 7, 8, and 13 TeV, as well as cosmic ray muon data collected during the periods when the LHC beams were not present. The present calibration is performed using the 13 TeV data collected during 2016 corresponding to an integrated luminosity of 35.9 fb(-1). The intercalibration of channels exploits the approximate uniformity of energy collection over the azimuthal angle. The absolute energy scale of the central and endcap calorimeters is set using isolated charged hadrons. The energy scale for the electromagnetic portion of the forward calorimeters is set using Z -> ee data. The energy scale of the outer calorimeters has been determined with test beam data and is confirmed through data with high transverse momentum jets. In this paper, we present the details of the calibration methods and accuracy.Öğe Calorimetric Measurements with Extremely Fine Spatial Resolution(IEEE, 2016) Bilki, Burak; Freund, Benjamin; Repond, JoseIn special tests, the active layers of the CALICE Digital Hadron Calorimeter prototype, the DHCAL, were exposed to low energy particle beams, without being interleaved by absorber plates. The thickness of each layer corresponded approximately to 0.29 radiation lengths or 0.034 nuclear interaction lengths, defined mostly by the copper and steel skins of the detector cassettes. With its extremely fine segmentation of the readout based on 1 x 1 cm(2) pads, the DHCAL provides unprecedented details of both electromagnetic and hadronic showers. This paper reports on measurements performed with this device in the Fermilab test beam with positrons in the energy range of 1 to 10 GeV. The measurements are compared to simulations based on GEANT4 and a standalone program to emulate the detailed response of the active elements.Öğe Calorimetry with Extremely Fine Spatial Segmentation(Institute of Physics, 2022) Bilki, Burak; vd.Particle Flow Algorithms (PFAs) attempt to measure each particle in a hadronic jet individually, using the detector subsystem that provides the best energy/momentum resolution. Calorimeters that can exploit the power of PFAs emphasize spatial granularity over single particle energy resolution. In this context, the CALICE Collaboration developed the Digital Hadron Calorimeter (DHCAL). The DHCAL uses Resistive Plate Chambers (RPCs) as active media and is read out with 1 ´ 1 cm2 pads and digital (1-bit) resolution. In order to obtain a unique dataset of electromagnetic and hadronic interactions with unprecedented spatial resolution, the DHCAL went through a broad test beam program. In addition to conventional calorimetry, the DHCAL offers detailed measurements of event shapes, rigorous tests of simulation models and various analytical tools to improve calorimetric performance. Here we report on the results from the analysis of DHCAL data and comparisons with the Monte Carlo simulationsÖğe Centrality And Pseudorapidity Dependence Of The Transverse Energy Density İn pPb Collisions At ?Snn = 5.02 Tev(The CMS Collaboration, 2019) Bilki, Burak; ., ve diğer.The almost hermetic coverage of the CMS detector is used to measure the distribution of transverse energy, ET, over 13.2 units of pseudorapidity, ?, for pPb collisions at a center-of-mass energy per nucleon pair of ?s NN = 5.02 TeV. The huge angular acceptance exploits the fact that the CASTOR calorimeter at ?6.6 < ? < ?5.2 is effectively present on both sides of the colliding system because of a switch in the protongoing and lead-going beam directions. This wide acceptance enables the study of correlations between well-separated angular regions and makes the measurement a particularly powerful test of event generators. For minimum bias pPb collisions the maximum value of dET/d? is 22 GeV, which implies an ET per participant nucleon pair comparable to that of peripheral PbPb collisions at ? s NN = 2.76 TeV. The increase of dET/d? with centrality is much stronger for the lead-going side than for the proton-going side. The ? dependence of dET/d? is sensitive to the ? range in which the centrality variable is defined. Several modern generators are compared to these results but none is able to capture all aspects of the ? and centrality dependence of the data and the correlations observed between different ? regions.Öğe Charged-Particle Angular Correlations İn Xexe Collisions At ?Snn = 5.44 TeV(The CMS Collaboration, 2019) Bilki, Burak; Gürpınar Güler, Emine; ., ve diğer.Azimuthal correlations of charged particles in xenon-xenon collisions at a center-of-mass energy per nucleon pair of ? sNN = 5.44 TeV are studied. The data were collected by the CMS experiment at the LHC with a total integrated luminosity of 3.42 ?b?1. The collective motion of the system formed in the collision is parametrized by a Fourier expansion of the azimuthal particle density distribution. The azimuthal anisotropy coefficients v2, v3, and v4 are obtained by the scalar-product, two-particle correlation, and multiparticle correlation methods.Within a hydrodynamic picture, these methods have different sensitivities to noncollective and fluctuation effects. The dependence of the Fourier coefficients on the size of the colliding system is explored by comparing the xenonxenon results with equivalent lead-lead data. Model calculations that include initial-state fluctuation effects are also compared to the experimental results. The observed angular correlations provide new constraints on the hydrodynamic description of heavy ion collisions.Öğe Charged-Particle Nuclear Modification Factors in XeXe Collisions at sNN????=5.44sNN=5.44 TeV(Springer Link, 2018) Bilki, Burak; ., ve digerThe differential yields of charged particles having pseudorapidity within |?| < 1 are measured using xenon-xenon (XeXe) collisions at sNN????=5.44sNN=5.44 TeV. The data, corresponding to an integrated luminosity of 3.42 ?b?1, were collected in 2017 by the CMS experiment at the LHC. The yields are reported as functions of collision centrality and transverse momentum, pT, from 0.5 to 100 GeV. A previously reported pT spectrum from proton-proton collisions at s?=5.02s=5.02TeV is used for comparison after correcting for the difference in center-of-mass energy. The nuclear modification factors using this reference, R AA * , are constructed and compared to previous measurements and theoretical predictions. In head-on collisions, the R AA * has a value of 0.17 in the pT range of 6–8 GeV, but increases to approximately 0.7 at 100 GeV. Above ?6 GeV, the XeXe data show a notably smaller suppression than previous results for lead-lead (PbPb) collisions at sNN????=5.02sNN=5.02 TeV when compared at the same centrality (i.e., the same fraction of total cross section). However, the XeXe suppression is slightly greater than that for PbPb in events having a similar number of participating nucleons.Öğe Combination Of Cms Searches For Heavy Resonances Decaying To Pairs Of Bosons Or Leptons(The CMS Collaboration, 2019) Gürpınar Güler, Emine; Bilki, Burak; ., ve diğer.A statistical combination of searches for heavy resonances decaying to pairs of bosons or leptons is presented. The data correspond to an integrated luminosity of 35.9 fb?1 collected during 2016 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. The data are found to be consistent with expectations from the standard model background. Exclusion limits are set in the context of models of spin-1 heavy vector triplets and of spin-2 bulk gravitons. For massdegenerate W0 and Z0 resonances that predominantly couple to the standard model gauge bosons, the mass exclusion at 95% confidence level of heavy vector bosons is extended to 4.5 TeV as compared to 3.8 TeV determined from the best individual channel. This excluded mass increases to 5.0 TeV if the resonances couple predominantly to fermions.Öğe Combination of inclusive and di erential t t charge asymmetry measurements using ATLAS and CMS data at p s = 7 and 8TeV(Springer Link, 2018) Bilki, BurakThis paper presents combinations of inclusive and di erential measurements of the charge asymmetry (AC) in top quark pair (t t) events with a lepton+jets signature by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at centreof- mass energies of 7 and 8TeV. The data correspond to integrated luminosities of about 5 and 20 fb?¹ for each experiment, respectively. The resulting combined LHC measurements of the inclusive charge asymmetry are ALHC7 C = 0:005 0:007 (stat) 0:006 (syst) at 7TeV and ALHC8 C = 0:0055 0:0023 (stat) 0:0025 (syst) at 8TeV. These values, as well as the combination of AC measurements as a function of the invariant mass of the t t system at 8TeV, are consistent with the respective standard model predictions.Öğe Combination Of Searches For Heavy Resonances Decaying To WW, WZ, ZZ, WH, And ZH Boson Pairs İn Proton-Proton Collisions At Root S=8 And 13 Tev(ScienceDirect, 2017) Bilki, Burak; ., ve digerA statistical combination of searches is presented for massive resonances decaying to WW, WZ, ZZ, WH, and ZH boson pairs in proton-proton collision data collected by the CMS experiment at the LHC. The data were taken at centre-of-mass energies of 8 and 13 TeV, corresponding to respective integrated luminosities of 19.7 and up to 2.7 fb?1 . The results are interpreted in the context of heavy vector triplet and singlet models that mimic properties of composite-Higgs models predicting W0 and Z0 bosons decaying to WZ, WW, WH, and ZH bosons. A model with a bulk graviton that decays into WW and ZZ is also considered. This is the first combined search for WW, WZ, WH, and ZH resonances and yields lower limits on masses at 95% confidence level for W0 and Z0 singlets at 2.3 TeV, and for a triplet at 2.4 TeV. The limits on the production cross section of a narrow bulk graviton resonance with the curvature scale of the warped extra dimension ˜k = 0.5, in the mass range of 0.6 to 4.0 TeV, are the most stringent published to date.Öğe Combination of Searches for Higgs Boson Pair Production in Proton-Proton Collisions at ? s = 13 TeV(The CMS Collaboration, 2019) Bilki, Burak; ., ve diğer.This Letter describes a search for Higgs boson pair production using the combined results from four final states: bb??, bb??, bbbb, and bbVV, where V represents a W or Z boson. The search is performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions at ffiffiffi ps ¼ 13 TeV, corresponding to an integrated luminosity of 35.9 fb?1. Limits are set on the Higgs boson pair production cross section. A 95% confidence level observed (expected) upper limit on the nonresonant production cross section is set at 22.2 (12.8) times the standard model value. A search for narrow resonances decaying to Higgs boson pairs is also performed in the mass range 250–3000 GeV. No evidence for a signal is observed, and upper limits are set on the resonance production cross section.Öğe Combination Of The W Boson Polarization Measurements İn Top Quark Decays Using Atlas And Cms Data At Root S=8 Tev(CMS Collaboration, 2020) Bilki, Burak; ., ve diğer.The combination of measurements of the W boson polarization in top quark decays performed by the ATLAS and CMS ollaborations is presented. The measurements are based on proton-proton collision data produced at the LHC at a centre-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of about 20 fb?1 for each experiment. The measurements used events containing one lepton and having different jet multiplicities in the final state. The results are quoted as fractions of W bosons with longitudinal (F0 ), left-handed (FL), or right-handed (FR) polarizations. The resulting combined measurements of the polarization fractions are F0 = 0.693 ± 0.014 and FL = 0.315 ± 0.011. The fraction FR is calculated from the unitarity constraint to be FR = ?0.008 ± 0.007. These results are in agreement with the standard model predictions at next-to-next-to-leading order in perturbative quantum chromodynamics and represent an improvement in precision of 25 (29)% for F0 (FL) with respect to the most precise single measurement. A limit on anomalous right-handed vector (VR), and left- and right-handed tensor (gL, gR) tWb couplings is set while fixing all others to their standard model values. The allowed regions are [?0.11, 0.16] for VR, [?0.08, 0.05] for gL, and [?0.04, 0.02] for gR, at 95% confidence level. Limits on the corresponding Wilson coefficients are also derived.Öğe Combinations Of Single-Top-Quark Production Cross-Section Measurements And |Flv Vtb| Determinations At ?s = 7 And 8 Tev With The Atlas And Cms Experiments(The CMS Collaboration, 2019) Bilki, Burak; Gürpınar Güler, Emine; ., ve diğer.This paper presents the combinations of single-top-quark production cross-section measurements by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at s? = 7 and 8 TeV corresponding to integrated luminosities of 1.17 to 5.1 fb?1 at s? = 7 TeV and 12.2 to 20.3 fb?1 at s? = 8 TeV. These combinations are performed per centre-of-mass energy and for each production mode: t-channel, tW, and s-channel. The combined t-channel cross-sections are 67.5 ± 5.7 pb and 87.7 ± 5.8 pb at s? = 7 and 8 TeV respectively. The combined tW cross-sections are 16.3 ± 4.1 pb and 23.1 ± 3.6 pb at s? = 7 and 8 TeV respectively. For the s-channel cross-section, the combination yields 4.9 ± 1.4 pb at s? = 8 TeV. The square of the magnitude of the CKM matrix element Vtb multiplied by a form factor fLV is determined for each production mode and centre-of-mass energy, using the ratio of the measured cross-section to its theoretical prediction. It is assumed that the top-quark-related CKM matrix elements obey the relation |Vtd|, |Vts| ? |Vtb|. All the |fLVVtb|2 determinations, extracted from individual ratios at s? = 7 and 8 TeV, are combined, resulting in |fLVVtb| = 1.02 ± 0.04 (meas.) ± 0.02 (theo.). All combined measurements are consistent with their corresponding Standard Model predictions.Öğe Combined Measurements of Higgs Boson Couplings in Proton–Proton Collisions at ? s = 13TeV(CMS Collaboration, 2019) Bilki, Burak; ., ve diğer.Combined measurements of the production and decay rates of the Higgs boson, as well as its couplings to vector bosons and fermions, are presented. The analysis uses the LHC proton–proton collision data set recorded with the CMS detector in 2016 at ?s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb?1. The combination is based on analyses targeting the five main Higgs boson production mechanisms (gluon fusion, vector boson fusion, and associated production with a W or Z boson, or a top quarkantiquark pair) and the following decay modes: H ? ??, ZZ, WW, ??, bb, and ??. Searches for invisible Higgs boson decays are also considered. The best-fit ratio of the signal yield to the standard model expectation is measured to be ? = 1.17 ± 0.10, assuming a Higgs boson mass of 125.09 GeV. Additional results are given for various assumptions on the scaling behavior of the production and decay modes, including generic parametrizations based on ratios of cross sections and branching fractions or couplings. The results are compatible with the standardmodel predictions in all parametrizations considered. In addition, constraints are placed on various two Higgs doublet models.
