Journal of High Energy Physics (Apr 2020)

A high efficiency photon veto for the Light Dark Matter eXperiment

  • The LDMX collaboration,
  • Torsten Åkesson,
  • Nikita Blinov,
  • Lene Bryngemark,
  • Owen Colegrove,
  • Giulia Collura,
  • Craig Dukes,
  • Valentina Dutta,
  • Bertrand Echenard,
  • Thomas Eichlersmith,
  • Craig Group,
  • Joshua Hiltbrand,
  • David G. Hitlin,
  • Joseph Incandela,
  • Gordan Krnjaic,
  • Juan Lazaro,
  • Amina Li,
  • Jeremiah Mans,
  • Phillip Masterson,
  • Jeremy McCormick,
  • Omar Moreno,
  • Geoffrey Mullier,
  • Akshay Nagar,
  • Timothy Nelson,
  • Gavin Niendorf,
  • James Oyang,
  • Reese Petersen,
  • Ruth Pöttgen,
  • Philip Schuster,
  • Harrison Siegel,
  • Natalia Toro,
  • Nhan Tran,
  • Andrew Whitbeck

DOI
https://doi.org/10.1007/JHEP04(2020)003
Journal volume & issue
Vol. 2020, no. 4
pp. 1 – 35

Abstract

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Abstract Fixed-target experiments using primary electron beams can be powerful discovery tools for light dark matter in the sub-GeV mass range. The Light Dark Matter eXperiment (LDMX) is designed to measure missing momentum in high-rate electron fixed-target reactions with beam energies of 4 GeV to 16 GeV. A prerequisite for achieving several important sensitivity milestones is the capability to efficiently reject backgrounds associated with few-GeV bremsstrahlung, by twelve orders of magnitude, while maintaining high efficiency for signal. The primary challenge arises from events with photo-nuclear reactions faking the missing-momentum property of a dark matter signal. We present a methodology developed for the LDMX detector concept that is capable of the required rejection. By employing a detailed Geant4-based model of the detector response, we demonstrate that the sampling calorimetry proposed for LDMX can achieve better than 10 −13 rejection of few-GeV photons. This suggests that the luminosity-limited sensitivity of LDMX can be realized at 4 GeV and higher beam energies.

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