Cosmological implications of photon-flux upper limits at ultrahigh energies in scenarios of Planckian-interacting massive particles for dark matter

THE PIERRE AUGER COLLABORATION (P HANSEN PERTENECE A LA COLABORACIÓN AUGER)

PHYSICAL REVIEW D - PARTICLE AND FILDS

American Physical Society.

Año: 2023 vol. 107

0556-2821

Using the data of the Pierre Auger Observatory, we report on a search for signatures that would besuggestive of super-heavy particles decaying in the Galactic halo. From the lack of signal, we present upperlimits for different energy thresholds above ≳108 GeV on the secondary by-product fluxes expected fromthe decay of the particles. Assuming that the energy density of these super-heavy particles matches that ofdark matter observed today, we translate the upper bounds on the particle fluxes into tight constraints on thecouplings governing the decay process as a function of the particle mass. Instantons, which arenonperturbative solutions to Yang-Mills equations, can give rise to decay channels otherwise forbiddenand transform stable particles into metastable ones. Assuming such instanton-induced decay processes, wederive a bound on the reduced coupling constant of gauge interactions in the dark sector: αX ≲ 0.09, for109 ≲ M X =GeV < 1019 . Conversely, we obtain that, for instance, a reduced coupling constant αX 1⁄4 0.09excludes masses MX ≳ 3 × 1013 GeV. In the context of dark matter production from gravitationalinteractions alone during the reheating epoch, we derive constraints on the parameter space that involves,in addition to M X and αX , the Hubble rate at the end of inflation, the reheating efficiency, and thenonminimal coupling of the Higgs with curvature.