Revisiting ultrahigh-energy constraints on decaying superheavy dark matter

We revisit constraints on decaying very heavy dark matter (VHDM) using the latest ultrahigh-energy cosmic-ray (UHECR; E greater than or similar to 1018 eV) data and ultrahigh-energy (UHE) gamma-ray flux upper limits, measured by the Pierre Auger Observatory. We present updated limits on the VHDM lifetime (tau chi) for masses up to-1015 GeV, considering decay into quarks, leptons, and massive bosons. In particular, we consider not only the UHECR spectrum but their composition data that favors heavier nuclei. Such a combined analysis improves the limits at less than or similar to 1012 GeV because VHDM decay does not produce UHECR nuclei. We also show that the constraints from the UHE gamma-ray upper limits are-10 more stringent than that obtained from cosmic rays, for all of the Standard Model final states we consider. The latter improves our limits to VHDM lifetime by a factor of two for dark matter mass greater than or similar to 1012 GeV.

Automated summary

In this study, constraints on decaying very heavy dark matter (VHDM) are revisited using the latest ultrahigh-energy cosmic-ray (UHECR) data and ultrahigh-energy (UHE) gamma-ray flux upper limits. Updated limits on the VHDM lifetime for masses up to 1015 GeV are presented, considering decay into quarks, leptons, and massive bosons. The analysis shows that the constraints from UHE gamma-ray upper limits are 10 times more stringent than those obtained from cosmic rays.