Searching for ultralight scalar dark matter with muonium and muonic atoms

TL;DR

This paper proposes using muonium and muonic atom spectroscopy to detect ultralight scalar dark matter, achieving sensitivity improvements over astrophysical bounds and exploring new force interactions.

Contribution

It introduces a novel method to search for ultralight scalar dark matter using muonium spectroscopy, surpassing previous bounds and probing new force interactions.

Findings

Spectroscopy can improve constraints on scalar-muon interactions by up to 12 orders of magnitude.

Free-fall experiments can probe forces from virtual ultralight scalar bosons, improving sensitivity by 5 orders.

Existing data already set stringent bounds on scalar-muon couplings.

Abstract

Ultralight scalar dark matter may induce apparent oscillations of the muon mass, which may be directly probed via temporal shifts in the spectra of muonium and muonic atoms. Existing datasets and ongoing spectroscopy measurements with muonium are capable of probing scalar-muon interactions that are up to 12 orders of magnitude more stringent than astrophysical bounds. Ongoing free-fall experiments with muonium can probe forces associated with the exchange of virtual ultralight scalar bosons between muons and standard-model particles, offering up to 5 orders of magnitude improvement in sensitivity over complementary laboratory and astrophysical bounds.