Searching for axion streams with the echo method

TL;DR

This paper explores the axion echo technique for dark matter detection, demonstrating enhanced sensitivity to local axion streams and discussing the potential of targeting Earth-focused dark matter hairs.

Contribution

It introduces the use of fine grained axion streams as targets, showing significant sensitivity improvements over the standard halo model in the echo detection method.

Findings

Sensitivity to axion-photon coupling improved up to two orders of magnitude.

Fine grained streams' small dispersion enhances echo method performance.

Potential to detect high density dark matter hairs near Earth.

Abstract

The axion dark matter echo technique, proposed in Ref. [1], aims to search for axion dark matter by detecting the electromagnetic echo coming from stimulated decay of ambient axion dark matter interacting with a radio-microwave outgoing beam. In this work we consider deviations from the standard halo model (SHM) in the form of fine grained streams that are present in the solar system and use them as a target for the axion echo method, which demonstrates to be very sensitive to particular local axion dark matter phase space distributions. We show that the extremely small dispersion of the streams works in favor of the echo method performance, improving its sensitivity in the axion-photon coupling up to two orders of magnitude, with respect to the isotropic SHM. We also discuss the possibility of targeting high density dark matter hairs formed when fine grained streams focus by the inner Earth's gravitational field.