Ultra High Energy Cosmic Rays & Super-heavy Dark Matter

TL;DR

This paper assesses how upcoming ultra-high energy cosmic ray experiments can detect anisotropies caused by decays of super-heavy dark matter, using simulations to evaluate the effectiveness of various observables.

Contribution

It identifies specific observables capable of revealing anisotropies from super-heavy dark matter and quantifies their performance through detailed Monte Carlo simulations.

Findings

Dipole observables can distinguish isotropic and anisotropic fluxes at 4-5 sigma confidence.

Forward-to-backward flux ratio is effective for large opening angles but less so with many events.

A 300-event experiment at 60 EeV has a 50% chance to detect anisotropy at 3 sigma significance.

Abstract

We reanalyse the prospects for upcoming Ultra-High Energy Cosmic Ray experiments in connection with the phenomenology of Super-heavy Dark Matter. We identify a set of observables well suited to reveal a possible anisotropy in the High Energy Cosmic Ray flux induced by the decays of these particles, and quantify their performance via Monte Carlo simulations that mimic the outcome of near-future and next-generation experiments. The spherical and circular dipoles are able to tell isotropic and anisotropic fluxes apart at a confidence level as large as $4\sigma$ or $5\sigma$, depending on the Dark Matter profile. The forward-to-backward flux ratio yields a comparable result for relatively large opening angles of about 40~deg, but it is less performing once a very large number of events is considered. We also find that an actual experiment employing these observables and collecting 300~events at 60~EeV would have a $50\%$ chance of excluding isotropy against Super-heavy Dark Matter at a significance of at least $3\sigma$