Identification of extreme energy photons with JEM-EUSO

A. D. SUPANITSKY; G MEDINA-TANCO

Conferencia; 33RD INTERNATIONAL COSMIC RAY CONFERENCE, RIO DE JANEIRO 2013 THE ASTROPARTICLE PHYSICS CONFERENCE; 2013

Extensive searches for ultra-high-energy photons have been performed by past and current cosmic-ray observatories. Nevertheless, at present no firm candidates have been found. All candidate events are compatible with proton primaries, which are the principal source of backgrounds for their identification. As a result, several upper limits on their integral photon flux have been obtained. Besides other theoretically possible sources, at least a flux of ultra-high-energy photons is expected as a result of the interactions suffered by cosmic rays during propagation through intergalactic medium. However, current upper limits do not reach the flux expected by the corresponding astrophysical models. Extreme Universe Space Observatory on board Japanese Experimental Module (JEM-EUSO), is an orbital fluorescence telescope intended to observe the most energetic component of cosmic rays (E > 10^19.7 eV), planned to be installed on the International Space Station. By design, the instrument is also sensitive to photons and neutrinos. In this work we study the potential of JEM-EUSO for photon searches. We obtain the upper limits on photon fractions in a total of expected events (under the assumption that there are no photons in the samples) for different combinations of observation time in the Nadir and Tilted modes of the telescope. For the calculation of the upper limits we use a statistical method based on the parameter Xmax, the atmospheric depth for which the maximum development of the shower of a primary particle is attained.