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

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

PHYSICAL REVIEW D

AMER PHYSICAL SOC

Lugar: New York; Año: 2023 vol. 107

1550-7998

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 ≲ MX=GeV < 1019. Conversely, we obtain that, for instance, a reduced coupling constant αX ¼ 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 MX and αX, the Hubble rate at the end of inflation, the reheating efficiency, and thenonminimal coupling of the Higgs with curvature.