Evaluation of the Primary Energy of UHE Photon-induced Atmospheric Showers from Ground Array Measurements

Pierre Billoir, Cecile Roucelle, Jean-Christophe Hamilton

A photon induced shower at $E_{prim}\ge 10^{18}$ eV exhibits very specific features and is different from a hadronic one. At such energies, the LPM effect delays in average the fir…