Measurement of the photon identification efficiencies with the ATLAS detector using LHC Run 2 data collected in 2015 and 2016

Research output: Contribution to journalArticlepeer-review


  • ATLAS Collaboration

Colleges, School and Institutes

External organisations

  • Université Mohamed Premier and LPTPM
  • CNRS/IN2P3
  • Institute of Physics Azerbaijan National Academy of Sciences
  • IN2P3
  • Royal Holloway, University of London
  • University of Toronto
  • Niels Bohr Institute
  • Tel Aviv University
  • Technion - Israel Institute of Technology
  • Argonne National Laboratory
  • Department of Physics and Astronomy and INFN
  • Abdus Salam International Centre for Theoretical Physics
  • Tokyo Metropolitan University
  • Johannes Gutenberg University
  • Electronics and Telecommunications
  • Northern Illinois University
  • University of Munich
  • Bogazici University
  • Santa Cruz Institute for Particle Physics
  • Alexandru Ioan Cuza University of Iasi
  • Laboratório de Instrumentação e Física Experimental de Partículas
  • Universidad de Granada
  • Université Paris-Saclay
  • University of Johannesburg
  • University of Sussex
  • European Organization for Nuclear Research (CERN)


The efficiency of the photon identification criteria in the ATLAS detector is measured using 36.1fb1 to 36.7fb1 of pp collision data at s=13 TeV collected in 2015 and 2016. The efficiencies are measured separately for converted and unconverted isolated photons, in four different pseudorapidity regions, for transverse momenta between 10 GeV and 1.5 TeV. The results from the combination of three data-driven techniques are compared with the predictions from simulation after correcting the variables describing the shape of electromagnetic showers in simulation for the average differences observed relative to data. Data-to-simulation efficiency ratios are determined to account for the small residual efficiency differences. These factors are measured with uncertainties between 0.5% and 5% depending on the photon transverse momentum and pseudorapidity. The impact of the isolation criteria on the photon identification efficiency, and that of additional soft pp interactions, are also discussed. The probability of reconstructing an electron as a photon candidate is measured in data, and compared with the predictions from simulation. The efficiency of the reconstruction of photon conversions is measured using a sample of photon candidates from Z→ μμγ events, exploiting the properties of the ratio of the energies deposited in the first and second longitudinal layers of the ATLAS electromagnetic calorimeter.

Bibliographic note

Aaboud, M., Aad, G., Abbott, B. et al. Eur. Phys. J. C (2019) 79: 205.


Original languageEnglish
Article number205
JournalEuropean Physical Journal C
Issue number3
Publication statusPublished - 7 Mar 2019