Tidal streams from axion miniclusters and direct axion searches

TL;DR

This paper explores how tidal streams from disrupted axion miniclusters could enhance signals in direct axion detection experiments, potentially impacting search strategies.

Contribution

It provides estimates of the fraction of disrupted miniclusters, stream parameters, and the expected rate of stream-crossing events affecting axion searches.

Findings

Stream-crossing events occur roughly once every 20 years.

During these events, axion signals could be amplified by a factor of about 10.

Tidal disruption of miniclusters may significantly influence direct axion detection efforts.

Abstract

In some axion dark matter models a dominant fraction of axions resides in dense small-scale substructures, axion miniclusters. A fraction of these substructures is disrupted and forms tidal streams where the axion density may still be an order of magnitude larger than the average. We discuss implications of these streams for the direct axion searches. We estimate the fraction of disrupted miniclusters and the parameters of the resulting streams, and find that stream-crossing events would occur at a rate of about $1/(20 {\rm yr})$ for 2-3 days, during which the signal in axion detectors would be amplified by a factor $\sim 10$. These estimates suggest that the effect of the tidal disruption of axion miniclusters may be important for direct axion searches and deserves a more thorough study.