In a Letter released to arXiv submitted to PRL, J. Biteau, A. Condorelli, O. Deligny, P. Ghia, I. Lhenry-Yvon, S. Marafico and T. Suomijärvi, with the collaboration of Pierre Auger, draw some consequences of the lack of detection of photons of energy higher than 100 PeV in terms of constraints on a hidden sector of superheavy particles, which could have been produced during the reheating era in the thermal history of the early universe and could possibly constitute the dark matter.
We investigate instanton-induced decay processes of super-heavy dark matter particles X produced during the inflationary epoch. Using data collected at the Pierre Auger Observatory we derive a bound on the reduced coupling constant of gauge interactions in the dark sector: αXeff ≤ 0.09, for 1010 < MX/GeV < 1016. We show that this upper limit on αXeff is complementary to that obtained from the non-observation of tensor modes in the cosmic microwave background.