Yazar "Ero, J." seçeneğine göre listele

Listeleniyor 1 - 4 / 4
  • [ X ]
    Öğe
    Constraints on the Initial State of Pb-Pb Collisions via Measurements of Z-Boson Yields and Azimuthal Anisotropy at √sNN=5.02 TeV
    (Amer Physical Soc, 2021) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Bergauer, T.; Dragicevic, M.; Ero, J.
    The CMS experiment at the LHC has measured the differential cross sections of Z bosons decaying to pairs of leptons, as functions of transverse momentum and rapidity, in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The measured Z boson elliptic azimuthal anisotropy coefficient is compatible with zero, showing that Z bosons do not experience significant final-state interactions in the medium produced in the collision. Yields of Z bosons are compared to Glauber model predictions and are found to deviate from these expectations in peripheral collisions, indicating the presence of initial collision geometry and centrality selection effects. The precision of the measurement allows, for the first time, for a data-driven determination of the nucleon-nucleon integrated luminosity as a function of lead-lead centrality, thereby eliminating the need for its estimation based on a Glauber model.
  • [ X ]
    Öğe
    First Search for Exclusive Diphoton Production at High Mass with Tagged Protons in Proton-Proton Collisions at √s=13 TeV
    (Amer Physical Soc, 2022) Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; Ero, J.; Del Valle, A. Escalante; Fruhwirth, R.
    A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp -> p gamma gamma p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb(-1) collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeVat the LHC. Events are selected with a diphoton invariant mass above 350 GeVand with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons match the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% confidence level are vertical bar zeta(1)vertical bar < 2.9 x 10(-1)3 GeV-4 and vertical bar zeta(2)vertical bar < 6.0 x 10(-13) GeV-4.
  • [ X ]
    Öğe
    Observation of Bs0 mesons and measurement of the Bs0/B+ yield ratio in PbPb collisions at √SNN=5.02 TeV
    (Elsevier, 2022) Tumasyan, A.; Adam, W.; Ambrogi, F.; Bergauer, T.; Dragicevic, M.; Ero, J.; Del Valle, A. Escalante
    The B-s(0) and B+ production yields are measured in PbPb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The data sample, collected with the CMS detector at the LHC, corresponds to an integrated luminosity of 1.7 nb(-1). The mesons are reconstructed in the exclusive decay channels B-s(0) -> J/psi (mu(+)mu(-))phi(K+K-) and B+ -> J/psi(mu(+)mu(-))K+ in the transverse momentum range 7-50 GeV/c and absolute rapidity 0-2.4. The B-s(0) meson is observed with a statistical significance in excess of five standard deviations for the first time in nucleus-nucleus collisions. The measurements are performed as functions of the transverse momentum of the B mesons and of the PbPb collision centrality. The ratio of production yields of B-s(0) and B+ is measured and compared to theoretical models that include quark recombination effects. (C) 2022 The Author(s). Published by Elsevier B.V.
  • [ X ]
    Öğe
    Search for a heavy vector resonance decaying to a Z boson and a Higgs boson in proton-proton collisions at s=13 Te
    (Springer, 2021) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; Ero, J.; Del Valle, A. Escalante
    A search is presented for a heavy vector resonance decaying into a Z boson and the standard model Higgs boson, where the Z boson is identified through its leptonic decays to electrons, muons, or neutrinos, and the Higgs boson is identified through its hadronic decays. The search is performed in a Lorentz-boosted regime and is based on data collected from 2016 to 2018 at the CERN LHC, corresponding to an integrated luminosity of 137 fb-1. Upper limits are derived on the production of a narrow heavy resonance Z ', and a mass below 3.5 and 3.7 Te is excluded at 95% confidence level in models where the heavy vector boson couples predominantly to fermions and to bosons, respectively. These are the most stringent limits placed on the Heavy Vector Triplet Z ' model to date. If the heavy vector boson couples exclusively to standard model bosons, upper limits on the product of the cross section and branching fraction are set between 23 and 0.3 fb for a Z ' mass between 0.8 and 4.6 Te, respectively. This is the first limit set on a heavy vector boson coupling exclusively to standard model bosons in its production and decay.