Searching for Earth/Solar Axion Halos

TL;DR

This paper explores how gravitationally bound axion halos around Earth or Sun could enhance detection sensitivity in axion dark matter experiments and produce unique, orientation-dependent signals.

Contribution

It introduces the concept of Earth/Solar axion halos and analyzes their impact on experimental sensitivity and signal characteristics.

Findings

Significant sensitivity gains possible with axion halos

Novel signals depend on detector orientation and location

Existing bounds are satisfied despite the halos' presence

Abstract

We discuss the sensitivity of the present and near-future axion dark matter experiments to a halo of axions or axion-like particles gravitationally bound to the Earth or the Sun. The existence of such halos, assuming they are formed, renders a significant gain in the sensitivity of axion searches while satisfying all the present experimental bounds. The structure and coherence properties of these halos also imply novel signals, which can depend on the latitude or orientation of the detector. We demonstrate this by analysing the sensitivity of several distinct types of axion dark matter experiments.