Yazar "Damanakis K." seçeneğine göre listele

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    Luminosity determination using Z boson production at the CMS experiment
    (Institute for Ionics, 2024) Hayrapetyan A.; Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.
    The measurement of Z boson production is presented as a method to determine the integrated luminosity of CMS data sets. The analysis uses proton–proton collision data, recorded by the CMS experiment at the CERN LHC in 2017 at a center-of-mass energy of 13 TeV . Events with Z bosons decaying into a pair of muons are selected. The total number of Z bosons produced in a fiducial volume is determined, together with the identification efficiencies and correlations from the same data set, in small intervals of 20 pb-1 of integrated luminosity, thus facilitating the efficiency and rate measurement as a function of time and instantaneous luminosity. Using the ratio of the efficiency-corrected numbers of Z bosons, the precisely measured integrated luminosity of one data set is used to determine the luminosity of another. For the first time, a full quantitative uncertainty analysis of the use of Z bosons for the integrated luminosity measurement is performed. The uncertainty in the extrapolation between two data sets, recorded in 2017 at low and high instantaneous luminosity, is less than 0.5%. We show that the Z boson rate measurement constitutes a precise method, complementary to traditional methods, with the potential to improve the measurement of the integrated luminosity. © 2024, The Author(s).
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    Measurement of the electroweak production of Formula Presented in association with two jets in proton-proton collisions at Formula Presented
    (American Physical Society, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; Dragicevic M.
    A measurement is presented for the electroweak production of a Formula Presented boson, a photon (Formula Presented), and two jets (j) in proton-proton collisions. The leptonic decay of the Formula Presented boson is selected by requiring one identified electron or muon and large missing transverse momentum. The two jets are required to have large invariant dijet mass and large separation in pseudorapidity. The measurement is performed with the data collected by the CMS detector at a center-of-mass energy of Formula Presented, corresponding to an integrated luminosity of Formula Presented. The cross section for the electroweak Formula Presented production is Formula Presented, whereas the total cross section for Formula Presented production is Formula Presented. Differential cross sections are also measured with the distributions unfolded to the particle level. All results are in agreement with the standard model expectations. Constraints are placed on anomalous quartic gauge couplings (aQGCs) in terms of dimension-8 effective field theory operators. These are the most stringent limits to date on the aQGCs parameters Formula Presented and Formula Presented. © 2023 CERN, for the CMS Collaboration.
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    Measurement of the production cross section for a W boson in association with a charm quark in proton–proton collisions at ?s=13TeV
    (Institute for Ionics, 2024) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; Dragicevic M.
    The strange quark content of the proton is probed through the measurement of the production cross section for a W boson and a charm (c) quark in proton–proton collisions at a center-of-mass energy of 13 TeV . The analysis uses a data sample corresponding to a total integrated luminosity of 138 fb-1 collected with the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm jets are tagged using the presence of a muon or a secondary vertex inside the jet. The W + c production cross section and the cross section ratio Rc±=?(W++c¯)/?(W-+c) are measured inclusively and differentially as functions of the transverse momentum and the pseudorapidity of the lepton originating from the W boson decay. The precision of the measurements is improved with respect to previous studies, reaching 1% in Rc±=0.950±0.005(stat)±0.010(syst) . The measurements are compared with theoretical predictions up to next-to-next-to-leading order in perturbative quantum chromodynamics. © 2024, The Author(s).
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    Probing Small Bjorken-x Nuclear Gluonic Structure via Coherent J=? Photoproduction in Ultraperipheral Pb-Pb Collisions at ?sNN = 5.02 TeV
    (American Physical Society, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; Dragicevic M.
    Quasireal photons exchanged in relativistic heavy ion interactions are powerful probes of the gluonic structure of nuclei. The coherent J=? photoproduction cross section in ultraperipheral lead-lead collisions is measured as a function of photon-nucleus center-of-mass energies per nucleon (WPb?N) over a wide range of 40 < WPb?N < 400 GeV. Results are obtained using data at the nucleon-nucleon center-of-mass energy of 5.02 TeV collected by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 1.52 nb?1. The cross section is observed to rise rapidly at low WPb?N, and plateau above WPb?N ? 40 GeV, up to 400 GeV, entering a new regime of small Bjorken-x (?6 × 10?5) gluons being probed in a heavy nucleus. The observed energy dependence is not predicted by current quantum chromodynamic models. © 2023 CERN, for the CMS Collaboration.
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    Search for Inelastic Dark Matter in Events with Two Displaced Muons and Missing Transverse Momentum in Proton-Proton Collisions at ?s=13 TeV
    (American Physical Society, 2024) Hayrapetyan A.; Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.
    A search for dark matter in events with a displaced nonresonant muon pair and missing transverse momentum is presented. The analysis is performed using an integrated luminosity of 138 fb-1 of protonproton (pp) collision data at a center-of-mass energy of 13 TeV produced by the LHC in 2016.2018. No significant excess over the predicted backgrounds is observed. Upper limits are set on the product of the inelastic dark matter production cross section ?(pp ? A? ? ?1?2) and the decay branching fraction ?(?2 ? ?1?+?-), where A? is a dark photon and +++?1 and ?2 are states in the dark sector with near mass degeneracy. This is the first dedicated collider search for inelastic dark matter. © 2024 American Physical Society. All rights reserved.
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    A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer
    (Institute for Ionics, 2023) Tumasyan A.; Adam W.; Andrejkovic J.W.; Bergauer T.; Chatterjee S.; Damanakis K.; Dragicevic M.
    A generic search is presented for the associated production of a Z boson or a photon with an additional unspecified massive particle X, pp ? pp + Z / ? + X , in proton-tagged events from proton–proton collisions at s=13TeV , recorded in 2017 with the CMS detector and the CMS-TOTEM precision proton spectrometer. The missing mass spectrum is analysed in the 600–1600 GeV range and a fit is performed to search for possible deviations from the background expectation. No significant excess in data with respect to the background predictions has been observed. Model-independent upper limits on the visible production cross section of pp ? pp + Z / ? + X are set. © 2023, The Author(s).