The potential of the JEM-EUSO telescope for the astrophysics of extreme energy photons

Extreme energy photons are expected to be a minor component of the ultra high energy cosmic rays. Nevertheless, they are the carriers of very important astrophysical information related to the origin and propagation of such ultra energetic particles. JEM-EUSO is an orbital fluorescence telescope intended to observe the highest energy component of the cosmic rays, including photons and neutrinos. In this work we study several techniques to improve the discrimination between photon and proton showers in the context of the JEM-EUSO telescope. The most important parameter used to discriminate between protons and gammas is the atmospheric depth of the maximum of the showers, Xmax. However, it can be demonstrated that, for a given available statistics, additional information is needed in order to take advantage of the full potential of the instrument. We propose and study additional parameters, related to the shape of the longitudinal profile, in order to obtain a better discrimination than the one given by Xmax alone.