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Measurement of photon–jet transverse momentum correlations in 5.02 TeV Pb + Pb and pp collisions with ATLAS

  • The ATLAS collaboration
  • Mohamed I University
  • Aix-Marseille Université
  • University of Oklahoma
  • Azerbaijan National Academy of Sciences
  • IN2P3/CNRS
  • Royal Holloway University of London
  • University of Toronto
  • University of Copenhagen
  • University of Sussex
  • Tel Aviv University
  • Technion-Israel Institute of Technology
  • Argonne National Laboratory
  • National Institute for Nuclear Physics
  • Abdus Salam International Centre for Theoretical Physics
  • The University of Tokyo
  • AGH University of Krakow
  • Northern Illinois University
  • Ludwig Maximilian University of Munich
  • Bogazici University
  • Rutherford Appleton Laboratory
  • University of California at Santa Cruz
  • Alexandru Ioan Cuza University of Iaşi
  • Laboratório de Instrumentação e Física Experimental de Partículas
  • University of Granada
  • Joint Institute for Nuclear Research
  • University of Rome Tor Vergata
  • Kyoto University
  • Lund University
  • University of Geneva
  • P.N. Lebedev Physical Institute of the Russian Academy of Sciences
  • University of Bologna
  • University of Victoria BC
  • Instituto de Física La Plata
  • Radboud University Nijmegen
  • CERN
  • Horia Hulubei National Institute of Physics and Nuclear Engineering
  • National Technical University of Athens
  • Czech Technical University in Prague
  • The University of Chicago
  • University of Washington

Research output: Contribution to journalArticlepeer-review

58 Scopus citations

Abstract

Jets created in association with a photon can be used as a calibrated probe to study energy loss in the medium created in nuclear collisions. Measurements of the transverse momentum balance between isolated photons and inclusive jets are presented using integrated luminosities of 0.49 nb−1 of Pb + Pb collision data at sNN=5.02 TeV and 25 pb−1 of pp collision data at s=5.02 TeV recorded with the ATLAS detector at the LHC. Photons with transverse momentum 63.1<pT γ<200 GeV and |ηγ|<2.37 are paired with all jets in the event that have pT jet>31.6 GeV and pseudorapidity |ηjet|<2.8. The transverse momentum balance given by the jet-to-photon pT ratio, x, is measured for pairs with azimuthal opening angle Δϕ>7π/8. Distributions of the per-photon jet yield as a function of x, (1/Nγ)(dN/dx), are corrected for detector effects via a two-dimensional unfolding procedure and reported at the particle level. In pp collisions, the distributions are well described by Monte Carlo event generators. In Pb + Pb collisions, the x distribution is modified from that observed in pp collisions with increasing centrality, consistent with the picture of parton energy loss in the hot nuclear medium. The data are compared with a suite of energy-loss models and calculations.

Original languageEnglish
Pages (from-to)167-190
Number of pages24
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume789
DOIs
StatePublished - Feb 10 2019

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