Non-Virialized Axion Search Sensitive to Doppler Effects in the Milky Way Halo

TL;DR

This paper reports the most sensitive search for non-virialized axions in the Milky Way halo, accounting for Doppler effects, and excludes certain relic axions with very low velocity dispersion.

Contribution

It introduces a novel search method for non-virialized axions considering Doppler shifts, extending the sensitivity beyond previous isothermal halo assumptions.

Findings

Excluded cold flow relic axions with velocity dispersion ~10^-7 c at 95% confidence

Conducted the most sensitive non-virialized axion search to date in the specified mass range

Demonstrated the importance of Doppler effects in axion detection sensitivity

Abstract

The Axion Dark Matter eXperiment (ADMX) has previously excluded Dine-Fischler-Srednicki-Zhitnisky (DFSZ) axions between 680-790 MHz under the assumption that the dark matter is described by the isothermal halo model. However, the precise nature of the velocity distribution of dark matter is still unknown, and alternative models have been proposed. We report the results of a non-virialized axion search over the mass range 2.81-3.31 {\mu}eV, corresponding to the frequency range 680-800 MHz. This analysis marks the most sensitive search for non-virialized axions sensitive to Doppler effects in the Milky Way Halo to date. Accounting for frequency shifts due to the detector's motion through the Galaxy, we exclude cold flow relic axions with a velocity dispersion of order 10^-7 c with 95% confidence.