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

Abstract

Using the data of the Pierre Auger Observatory, we report on a search for signatures that would be suggestive of super-heavy particles decaying in the Galactic halo. From the lack of signal, we present upper limits for different energy thresholds above ≳10 8 GeV on the secondary by-product fluxes expected from the decay of the particles. Assuming that the energy density of these super-heavy particles matches that of dark matter observed today, we translate the upper bounds on the particle fluxes into tight constraints on the couplings governing the decay process as a function of the particle mass. Instantons, which are nonperturbative solutions to Yang-Mills equations, can give rise to decay channels otherwise forbidden and transform stable particles into metastable ones. Assuming such instanton-induced decay processes, we derive a bound on the reduced coupling constant of gauge interactions in the dark sector: α X ≲ 0.09, for 10 9 ≲ M X =GeV < 10 19 . Conversely, we obtain that, for instance, a reduced coupling constant α X ¼ 0.09 excludes masses M X ≳ 3 × 10 13 GeV. In the context of dark matter production from gravitational interactions alone during the reheating epoch, we derive constraints on the parameter space that involves, in addition to M X and α X , the Hubble rate at the end of inflation, the reheating efficiency, and the nonminimal coupling of the Higgs with curvature.

Constraints on the proton fraction of cosmic rays at the highest energies and the consequences for cosmogenic neutrinos and photons

“…We do not investigate the SHDM scenario further, however, we wish to point out several key differences compared to our assumed source model. If the additional protons are produced in the decay of super-heavy dark matter, a substantial anisotropy in arrival directions and extremely local production of the observed UHECRs should be expected since the signal is predicted to be dominated by dark matter in the Milky Way with a particular clustering around the Galactic centre [73]. This is in sharp contrast to our proposed continuous distribution of sources in redshift up to z max = 4 and minimum source distance of ∼ 4 Mpc.…”

Searches for connections between dark matter and high-energy neutrinos with IceCube

“…Renewed interest in superheavy dark matter originates from the fact that collider-based searches came back empty-handed, and the superheavy dark matter region became experimentally accessible using high-energy neutrinos [168][169][170][171][172][173]. A comprehensive discussion on cosmological implications of ultra-long lifetimes for models with larger dark matter masses is presented in [174].…”

“Ultra-High-Energy Cosmic-Rays (UHECR): at the Intersection of the Cosmic and Energy Frontiers” -- Overview of the Snowmass UHECR white paper and roadmap

“…By selecting the air showers more likely to arise from lighter primaries, composition-enhanced anisotropy studies will be possible. Moreover, the huge exposure will allow probing further past the flux suppression in search of BSM physics, including Lorentz Invariance Violation (LIV) [34] and Super-Heavy Dark Matter (SHDM) candidates [35,36].…”