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

Abstract

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 10^18.5 to 10^19.6 eV. 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.

9 pages, 19 Figures. Accepted in Astroparticle Physics on May 31th, 2013

References in corpus (8)

• Measurement of the energy spectrum of cosmic rays above 10^18 eV using the Pierre Auger Observatory
• The Offline Software Framework of the Pierre Auger Observatory
• The Pierre Auger Observatory II: Studies of Cosmic Ray Composition and Hadronic Interaction models
• A new composition-sensitive parameter for Ultra-High Energy Cosmic Rays
• The Pierre Auger Observatory III: Other Astrophysical Observations
• Characteristics of geomagnetic cascading of ultra-high energy photons at the southern and northern sites of the Pierre Auger Observatory
• Pierre Auger Data, Photons, and Top-Down Cosmic Ray Models
• Evaluation of the Primary Energy of UHE Photon-induced Atmospheric Showers from Ground Array Measurements

Cited by in corpus (4)

• Constraints on the diffuse photon flux with energies above $10^{18}$ eV using the surface detector of the Telescope Array experiment
• Search for point sources of ultra-high energy photons with the Telescope Array surface detector
• Energy reconstruction of hadron-initiated showers of ultra-high energy cosmic rays
• $F_{\gamma }$: a new observable for photon-hadron discrimination in hybrid air shower events