Heavy Quark Production in Ultra High Energy Cosmic Ray Interactions
  In this paper we present a comprehensive study of the heavy quark production in ultra high energy cosmic ray interactions in the atmosphere considering that the primary cosmic ray can be either a photon, neutrino or a proton. The analysis is performed using a unified framework -- the dipole formalism --- and the saturation effects, associated to the physical process of parton recombination, are taken into account. We demonstrate that the contribution of heavy quarks for cosmic ray interactions is in general non-negligible and can be dominant depending of the process considered. Moreover, our results indicate that new dynamical mechanisms should be included in order to obtain reliable predictions for the heavy quark production in $pp$ collisions at ultra high cosmic ray energies. 
V.P. Goncalves, D. R. Gratieri
hep-ph astro-ph.HE hep-ex