Search for a Non-Relativistic Component in the Spectrum of Cosmic Rays at Earth

TL;DR

This paper describes a novel search method for non-relativistic dark matter particles at Earth, aiming to identify their unique speed distribution and interaction signatures, and reports the first limits for light dark matter particles.

Contribution

It introduces a new technique to detect slow-moving dark matter particles via cosmic ray analysis, including the first constraints on sub-100 MeV/c² dark matter interactions.

Findings

First limits set for dark matter lighter than 100 MeV/c²

Technique can discriminate dark matter from known particles

Potential to identify interaction types (nuclear vs. electron)

Abstract

Dark matter particles gravitationally bound to our galaxy should exhibit a characteristic speed distribution limited by their escape velocity at the position of the Earth ($v_{esc}\simeq$ 550 km/s). An ongoing search for anomalous cosmic rays at Earth, kinematically similar to cold dark matter, is described. The technique can discriminate between these and known slow-moving particles such as neutrons, would be sensitive to telltale signatures from presently unexplored candidates, and offers the possibility of identifying the mediating type of interaction (nuclear vs. electron recoils). Studies of background identification and abatement in a shallow underground site are presented. The expected reach of the method is discussed, and illustrated by obtaining the first limits for dark matter particles lighter than 100 MeV/c$^{2}$ interacting via nuclear recoils.