(American Physical Society, 2024-04-08) Binet, V.; Micheletti, M. I.; The Pierre Auger collaboration
Dark matter particles could be superheavy, provided their lifetime is much longer than the age of the Universe. Using the sensitivity of the Pierre Auger Observatory to ultrahigh energy neutrinos and photons, we constrain a specific extension of the Standard Model of particle physics that meets the lifetime requirement for a superheavy particle by coupling it to a sector of ultralight sterile neutrinos. Our results show that, for a typical dark coupling constant of 0.1, the mixing angle θm between active and sterile neutrinos must satisfy, roughly, θm ≲ 1.5 × 10−6ðMX=109 GeVÞ−2 for a mass MX of the dark-matter particle between 108 GeV and 1011 GeV.