Improving photon-hadron discrimination based on cosmic ray surface detector data

• Published in: Astroparticle physics 2013-07, Vol.47, p.10-17
• Main Authors: Ros, G., Supanitsky, A.D., Medina-Tanco, G.A., del Peral, L., Rodríguez-Frías, M.D.
• Format: Article
• Language: English
• Subjects: [formula omitted] parameter; Cherenkov detectors; Cosmic rays; Photon discrimination
• ISSN: 0927-6505; 1873-2852
• DOI: 10.1016/j.astropartphys.2013.05.014

•The parameter Sb is optimized for photon-hadron discrimination in cosmic ray surface arrays.•The discrimination capability (η) maximizes for b ∼ 3 for several array sizes and geometries.•If muon contribution is enhanced, optimal b is still 3 and η increases.•S3 is almost full-efficient above the energy threshold of the detector.•Minimum quality cuts are needed in a real experiment. The search for photons at EeV energies and beyond has considerable astrophysical interest and will remain one of the key challenges for ultra-high energy cosmic ray (UHECR) observatories in the near future. Several upper limits to the photon flux have been established since no photon has been unambiguously observed up to now. An improvement in the reconstruction efficiency of the photon showers and/or better discrimination tools are needed to improve these limits apart from an increase in statistics. Following this direction, we analyze in this work the ability of the surface parameter Sb, originally proposed for hadron discrimination, for photon search. Semi-analytical and numerical studies are performed in order to optimize Sb for the discrimination of photons from a proton background in the energy range from 1018.5 to 1019.6eV. Although not shown explicitly, the same analysis has been performed for Fe nuclei and the corresponding results are discussed when appropriate. The effects of different array geometries and the underestimation of the muon component in the shower simulations are analyzed, as well as the Sb dependence on primary energy and zenith angle.