Yazar "Damanakis, K." seçeneğine göre listele

Listeleniyor 1 - 20 / 53
  • Küçük Resim Yok
    Öğe
    Azimuthal anisotropy of dijet events in PbPb collisions at ?sNN=5.02 TeV
    (Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    The path-length dependent parton energy loss within the dense partonic medium created in lead-lead collisions at a nucleon-nucleon center-of-mass energy of root s(NN) = 5.02TeV is studied by determining the azimuthal anisotropies for dijets with high transverse momentum. The data were collected by the CMS experiment in 2018 and correspond to an integrated luminosity of 1.69 nb(-1). For events containing back-to-back jets, correlations in relative azimuthal angle and pseudorapidity (eta) between jets and hadrons, and between two hadrons, are constructed. The anisotropies are expressed as the Fourier expansion coefficients v(n), n = 2-4 of these azimuthal distributions. The dijet v(n) values are extracted from long-range (1.5 < vertical bar Delta eta vertical bar < 2.5) components of these correlations, which suppresses the background contributions from jet fragmentation processes. Positive dijet v(2) values are observed which increase from central to more peripheral events, while the v(3) and v(4) values are consistent with zero within experimental uncertainties.
  • Küçük Resim Yok
    Öğe
    Evidence for four-top quark production in proton-proton collisions at ?s=13 TeV
    (Elsevier, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    The production of four top quarks (tt over bar tt over bar ) is studied with LHC proton-proton collision data samples collected by the CMS experiment at a center-of-mass energy of 13 TeV, and corresponding to integrated luminosities of up to 138 fb-1. Events that have no leptons (all-hadronic), one lepton, or two oppositesign leptons (where lepton refers only to prompt electrons or prompt muons) are considered. This is the first tt over bar tt over bar measurement that includes the all-hadronic final state. The observed significance of the tt over bar tt over bar signal in these final states of 3.9 standard deviations (1.5 expected) provides evidence for tt over bar tt over bar production, with a measured cross section of 36+12 signal significance is 4.0 standard deviations (3.2 expected). The combination returns an observed cross section of 17 +/- 4 (stat) +/- 3 (syst) fb, which is consistent with the standard model prediction. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.
  • Küçük Resim Yok
    Öğe
    First measurement of the top quark pair production cross section in proton-proton collisions at ?s=13.6 TeV
    (Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    The first measurement of the top quark pair (t (t) over bar) production cross section in proton-proton collisions at root s = 13.6TeV is presented. Data recorded with the CMS detector at the CERN LHC in Summer 2022, corresponding to an integrated luminosity of 1.21 fb(-1), are analyzed. Events are selected with one or two charged leptons (electrons or muons) and additional jets. A maximum likelihood fit is performed in event categories defined by the number and flavors of the leptons, the number of jets, and the number of jets identified as originating from b quarks. An inclusive t (t) over bar production cross section of 881 +/- 23 (stat + syst) +/- 20 (lumi) pb is measured, in agreement with the standard model prediction of 924(-40)(+32) pb.
  • Küçük Resim Yok
    Öğe
    Higher-order moments of the elliptic flow distribution in PbPb collisions at sNN = 5.02 TeV
    (Springer Science and Business Media Deutschland GmbH, 2024) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    The hydrodynamic flow-like behavior of charged hadrons in high-energy lead-lead collisions is studied through multiparticle correlations. The elliptic anisotropy values based on different orders of multiparticle cumulants, v2{2k}, are measured up to the tenth order (k = 5) as functions of the collision centrality at a nucleon-nucleon center-of-mass energy of sNN = 5.02 TeV. The data were recorded by the CMS experiment at the LHC and correspond to an integrated luminosity of 0.607 nb?1. A hierarchy is observed between the coefficients, with v2{2} > v2{4} ? v2{6} ? v2{8} ? v2{10}. Based on these results, centrality-dependent moments for the fluctuation-driven event-by-event v2 distribution are determined, including the skewness, kurtosis and, for the first time, superskewness. Assuming a hydrodynamic expansion of the produced medium, these moments directly probe the initial-state geometry in high-energy nucleus-nucleus collisions. © The Author(s) 2024.
  • Küçük Resim Yok
    Öğe
    Measurement of inclusive and differential cross sections for single top quark production in association with a W boson in proton-proton collisions at ?s=13TeV
    (Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    Measurements of the inclusive and normalised differential cross sections are presented for the production of single top quarks in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13TeV. The data used were recorded with the CMS detector at the LHC during 2016-2018, and correspond to an integrated luminosity of 138 fb(-1). Events containing one electron and one muon in the final state are analysed. For the inclusive measurement, a multivariate discriminant, exploiting the kinematic properties of the events is used to separate the signal from the dominant t (t) over bar background. A cross section of 79.2 +/- 0.9 (stat)(-8.0)(+7.7) (syst) +/- 1.2 (lumi) pb is obtained, consistent with the predictions of the standard model. For the differential measurements, a fiducial region is defined according to the detector acceptance, and the requirement of exactly one jet coming from the fragmentation of a bottom quark. The resulting distributions are unfolded to particle level and agree with the predictions at next-to-leading order in perturbative quantum chromodynamics.
  • Küçük Resim
    Öğe
    Measurement of simplified template cross sections of the Higgs boson produced in association with W or Z bosons in the H → bb decay channel in proton-proton collisions at √s=13 TeV
    (American Physical Society, 2024) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    Differential cross sections are measured for the standard model Higgs boson produced in association with vector bosons (Formula Presented, Formula Presented) and decaying to a pair of Formula Presented quarks. Measurements are performed within the framework of the simplified template cross sections. The analysis relies on the leptonic decays of the Formula Presented and Formula Presented bosons, resulting in final states with 0, 1, or 2 electrons or muons. The Higgs boson candidates are either reconstructed from pairs of resolved Formula Presented-tagged jets, or from single large-radius jets containing the particles arising from two Formula Presented quarks. Proton-proton collision data at Formula Presented, collected by the CMS experiment in 2016-2018 and corresponding to a total integrated luminosity of Formula Presented, are analyzed. The inclusive signal strength, defined as the product of the observed production cross section and branching fraction relative to the standard model expectation, combining all analysis categories, is found to be Formula Presented. This corresponds to an observed (expected) significance of 6.3 (5.6) standard deviations.
  • Küçük Resim Yok
    Öğe
    Measurement of the Bs0 = ?+?- decay properties and search for the B0 ? ?+?- decay in proton-proton collisions at ?s=13 TeV
    (Elsevier, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    Measurements are presented of the B0s & RARR; & mu;+& mu;- branching fraction and effective lifetime, as well as results of a search for the B0 & RARR; & mu;+& mu;- decay in proton-proton collisions at & RADIC;s =13 TeV at the LHC. The analysis is based on data collected with the CMS detector in 2016-2018 corresponding to an integrated luminosity of 140 fb-1. The branching fraction of the B0s & RARR; & mu;+& mu;- decay and the effective B0s meson lifetime are the most precise single measurements to date. No evidence for the B0 & RARR; & mu;+& mu;- decay has been found. All results are found to be consistent with the standard model predictions and previous measurements. & COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.
  • Küçük Resim Yok
    Öğe
    Measurement of the cross section of top quark-antiquark pair production in association with a W boson in proton-proton collisions at ?s=13 TeV
    (Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    The production of a top quark-antiquark pair in association with a W boson (t (t) over barW) is measured in proton-proton collisions at a center-of-mass energy of 13TeV. The analyzed data was recorded by the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 138 fb(-1). Events with two or three leptons (electrons and muons) and additional jets are selected. In events with two leptons, a multiclass neural network is used to distinguish between the signal and background processes. Events with three leptons are categorized based on the number of jets and of jets originating from b quark hadronization, and the lepton charges. The inclusive t (t) over barW(+) production cross section in the full phase space is measured to be 868 +/- 40(stat)+/- 51(syst) fb. The t (t) over barW(+) and t (t) over barW(-) cross sections are also measured as 553 +/- 30(stat)+/- 30(syst) and 343 +/- 26(stat)+/- 25(syst) fb, respectively, and the corresponding ratio of the two cross sections is found to be 1.61 +/- 0.15(stat)(-0.05)(+0.07)(syst). The measured cross sections are larger than but consistent with the standard model predictions within two standard deviations, and represent the most precise measurement of these cross sections to date.
  • Küçük Resim Yok
    Öğe
    Measurement of the Dependence of the Hadron Production Fraction Ratios fs/fu and fd/fu on B Meson Kinematic Variables in Proton-Proton Collisions at ?s=13 TeV
    (Amer Physical Soc, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    The dependence of the ratio between the B-s(0) and B+ hadron production fractions, f(s)/f(u), on the transverse momentum (p(T)) and rapidity of the B mesons is studied using the decay channels B-s(0) -> J/psi phi and B+ -> J/psi K+. The analysis uses a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of 61.6 fb(-1). The f(s)/f(u) ratio is observed to depend on the B p(T) and to be consistent with becoming asymptotically constant at large p(T). No rapidity dependence is observed. The ratio of the B-0 to B+ meson production fractions, f(d)/f(u), is also measured, for the first time in proton-proton collisions, using the B-0 -> J/psi K*(0) decay channel. The result is found to be within 1 standard deviation of unity and independent of p(T) and rapidity, as expected from isospin invariance.
  • Küçük Resim Yok
    Öğe
    Measurement of the differential t(t)over-bar production cross section as a function of the jet mass and extraction of the top quark mass in hadronic decays of boosted top quarks
    (Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    A measurement of the jet mass distribution in hadronic decays of Lorentz-boosted top quarks is presented. The measurement is performed in the lepton + jets channel of top quark pair production (t (t) over bar) events, where the lepton is an electron or muon. The products of the hadronic top quark decay are reconstructed using a single large-radius jet with transverse momentum greater than 400GeV. The data were collected with the CMS detector at the LHC in proton-proton collisions and correspond to an integrated luminosity of 138fb(-1). The differential t (t) over bar production cross section as a function of the jet mass is unfolded to the particle level and is used to extract the top quark mass. The jet mass scale is calibrated using the hadronic W boson decay within the large-radius jet. The uncertainties in the modelling of the final state radiation are reduced by studying angular correlations in the jet substructure. These developments lead to a significant increase in precision, and a top quark mass of 173.06 +/- 0.84 GeV.
  • Küçük Resim Yok
    Öğe
    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.
  • Küçük Resim Yok
    Öğe
    Measurement of the Higgs boson inclusive and differential fiducial production cross sections in the diphoton decay channel with pp collisions at ?s=13 TeV
    (Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    The measurements of the inclusive and differential fiducial cross sections of the Higgs boson decaying to a pair of photons are presented. The analysis is performed using proton-proton collisions data recorded with the CMS detector at the LHC at a centre-of-mass energy of 13TeV and corresponding to an integrated luminosity of 137 fb(-1). The inclusive fiducial cross section is measured to be sigma(fid) = 73.4(-5.3)(+5.4)(stat)(+2.4)(-2.2)(syst) fb, in agreement with the standard model expectation of 75.4 +/- 4.1 fb. The measurements are also performed in fiducial regions targeting different production modes and as function of several observables describing the diphoton system, the number of additional jets present in the event, and other kinematic observables. Two double differential measurements are performed. No significant deviations from the standard model expectations are observed.
  • Küçük Resim Yok
    Öğe
    Measurement of the production cross section for a W boson in association with a charm quark in proton–proton collisions at ?s=13TeV
    (Springer Nature, 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).
  • Küçük Resim Yok
    Öğe
    Measurement of the t(t)over-bar charge asymmetry in events with highly Lorentz-boosted in collisions at ?s=13 TeV
    (Elsevier, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    The measurement of the charge asymmetry in top quark pair events with highly Lorentz-boosted top quarks decaying to a single lepton and jets is presented. The analysis is performed using protonproton collisions at root s = 13 TeV with the CMS detector at the LHC and corresponding to an integrated luminosity of 138 fb(-1). The selection is optimized for top quarks produced with large Lorentz boosts, resulting in nonisolated leptons and overlapping jets. The top quark charge asymmetry is measured for events with a t (t) over bar invariant mass larger than 750 GeV and corrected for detector and acceptance effects using a binned maximum likelihood fit. The measured top quark charge asymmetry of (0.42(-0.69)(+0.64))% is in good agreement with the standard model prediction at next-to-next-to-leading order in quantum chromodynamic perturbation theory with next-to-leading-order electroweak corrections. The result is also presented for two invariant mass ranges, 750-900 and >900 GeV. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
  • Küçük Resim Yok
    Öğe
    Measurement of the top quark mass using a profile likelihood approach with the lepton + jets final states in proton–proton collisions at ?s=13TeV
    (Institute for Ionics, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    The mass of the top quark is measured in 36.3 fb-1 of LHC proton–proton collision data collected with the CMS detector at s=13TeV . The measurement uses a sample of top quark pair candidate events containing one isolated electron or muon and at least four jets in the final state. For each event, the mass is reconstructed from a kinematic fit of the decay products to a top quark pair hypothesis. A profile likelihood method is applied using up to four observables per event to extract the top quark mass. The top quark mass is measured to be 171.77±0.37GeV . This approach significantly improves the precision over previous measurements. © 2023, The Author(s).
  • Küçük Resim Yok
    Öğe
    Measurement of the top quark pole mass using t(t)over-bar+jet events in the dilepton final state in proton-proton collisions at ?s=13 TeV
    (Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    A measurement of the top quark pole mass m(t)(pole) in events where a top quarkantiquark pair (t (t) over bar) is produced in association with at least one additional jet ( t (t) over bar +jet) is presented. This analysis is performed using proton-proton collision data at root s = 13TeV collected by the CMS experiment at the CERN LHC, corresponding to a total integrated luminosity of 36.3 fb(-1). Events with two opposite-sign leptons in the final state (e(+) e(-), mu(+) mu(-), e(+/-) mu(-/+)) are analyzed. The reconstruction of the main observable and the event classification are optimized using multivariate analysis techniques based on machine learning. The production cross section is measured as a function of the inverse of the invariant mass of the t t +jet system at the parton level using a maximum likelihood unfolding. Given a reference parton distribution function (PDF), the top quark pole mass is extracted using the theoretical predictions at next-to-leading order. For the ABMP16NLO PDF, this results in m(t)(pole) = 172.93 +/- 1.36 GeV.
  • Küçük Resim Yok
    Öğe
    Measurements of azimuthal anisotropy of nonprompt D0 mesons in PbPb collisions at ?sNN=5.02 TeV
    (Elsevier, 2024) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    Measurements of the elliptic (v(2)) and triangular (v(3)) azimuthal anisotropy coefficients are presented for D-0 mesons produced in b hadron decays (nonprompt D-0 mesons) in lead-lead collisions at root s(NN) = 5.02 TeV. The results are compared with previously published charm meson anisotropies measured using prompt D-0 mesons. The data were collected with the CMS detector in 2018 with an integrated luminosity of 0.58 nb(-1). Azimuthal anisotropy is sensitive to the interactions of quarks with the hot and dense medium created in heavy ion collisions. Comparing results for prompt and nonprompt D-0 mesons can assist in understanding the mass dependence of these interactions. The nonprompt results show lower magnitudes of v(2) and v(3) and weaker dependences on the meson transverse momentum and collision centrality than those found for prompt D-0 mesons. The results are in agreement with theoretical predictions that include a mass dependence in the interactions of quarks with the medium.
  • Küçük Resim Yok
    Öğe
    Measurements of the azimuthal anisotropy of prompt and nonprompt charmonia in PbPb collisions at ?sNN=5.02 TeV
    (Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    The second-order (v(2)) and third-order (v(3)) Fourier coefficients describing the azimuthal anisotropy of prompt and nonprompt (from b-hadron decays) J/psi, as well as prompt psi(2S) mesons are measured in lead-lead collisions at a center-of-mass energy per nucleon pair of root s(NN) = 5.02TeV. The analysis uses a data set corresponding to an integrated luminosity of 1.61 nb(-1) recorded with the CMS detector. The J/psi and psi(2S) mesons are reconstructed using their dimuon decay channel. The v(2) and v(3) coefficients are extracted using the scalar product method and studied as functions of meson transverse momentum and collision centrality. The measured v(2) values for prompt J/psi mesons are found to be larger than those for nonprompt J/psi mesons. The prompt J/psi v(2) values at high pT are found to be underpredicted by a model incorporating only parton energy loss effects in a quark-gluon plasma medium. Prompt and nonprompt J/psi meson v(3) and prompt psi(2S) v(2) and v(3) values are also reported for the first time, providing new information about heavy quark interactions in the hot and dense medium created in heavy ion collisions.
  • Küçük Resim Yok
    Öğe
    Measurements of the Higgs boson production cross section and couplings in the W boson pair decay channel in proton-proton collisions at ?s=13TeV
    (Springer, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    Production cross sections of the standard model Higgs boson decaying to a pair of W bosons are measured in proton-proton collisions at a center-of-mass energy of 13 TeV. The analysis targets Higgs bosons produced via gluon fusion, vector boson fusion, and in association with a W or Z boson. Candidate events are required to have at least two charged leptons and moderate missing transverse momentum, targeting events with at least one leptonically decaying W boson originating from the Higgs boson. Results are presented in the form of inclusive and differential cross sections in the simplified template cross section framework, as well as couplings of the Higgs boson to vector bosons and fermions. The data set collected by the CMS detector during 2016-2018 is used, corresponding to an integrated luminosity of 138 fb(-1). The signal strength modifier mu, defined as the ratio of the observed production rate in a given decay channel to the standard model expectation, is measured to be mu = 0.95(-0.09)(+0.10). All results are found to be compatible with the standard model within the uncertainties.
  • Küçük Resim Yok
    Öğe
    Observation of ? Lepton Pair Production in Ultraperipheral Pb-Pb Collisions at ?sNN=5.02 TeV
    (Amer Physical Soc, 2023) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.
    We present an observation of photon-photon production of t lepton pairs in ultraperipheral lead-lead collisions. The measurement is based on a data sample with an integrated luminosity of 404 mu b(-1) collected by the CMS experiment at a center-of-mass energy per nucleon pair of root s(NN) = 5.02 TeV. The gamma gamma -> tau(+)tau(-) process is observed for tau(+)tau(-) events with a muon and three charged hadrons in the final state. The measured fiducial cross section is sigma(gamma gamma ->tau(+)tau(-)) = 4.8 +/- 0.6(stat) +/- 0.5(syst) mu b, where the second (third) term corresponds to the statistical (systematic) uncertainty in sigma(gamma gamma ->tau(+)tau(-)) in agreement with leading-order QED predictions. Using sigma(gamma gamma ->tau(+)tau(-)), we estimate a model-dependent value of the anomalous magnetic moment of the t lepton of at a(tau) = 0.001(-0.089)(+0.055).