Global anisotropy of arrival directions of ultra-high-energy cosmic rays: capabilities of space-based detectors

TL;DR

This paper evaluates the potential of space-based detectors like TUS, JEM-EUSO, and S-EUSO to detect large-scale anisotropies in ultra-high-energy cosmic rays, focusing on models related to galaxy and dark matter distributions.

Contribution

It provides a quantitative analysis of anisotropy strengths for different cosmic-ray origin models and suggests optimal strategies for future space-based observations.

Findings

Space-based detectors can observe the full sky for anisotropy detection.

Anisotropy signals differ between extragalactic and dark matter models.

Optimal search strategies depend on detector exposure and model specifics.

Abstract

Planned space-based ultra-high-energy cosmic-ray detectors (TUS, JEM-EUSO and S-EUSO) are best suited for searches of global anisotropies in the distribution of arrival directions of cosmic-ray particles because they will be able to observe the full sky with a single instrument. We calculate quantitatively the strength of anisotropies associated with two models of the origin of the highest-energy particles: the extragalactic model (sources follow the distribution of galaxies in the Universe) and the superheavy dark-matter model (sources follow the distribution of dark matter in the Galactic halo). Based on the expected exposure of the experiments, we estimate the optimal strategy for efficient search of these effects.