Precision Muonium Spectroscopy

TL;DR

This paper discusses precision spectroscopy of muonium, a simple leptonic atom, to test fundamental physics, determine constants, and explore new physics phenomena like antimatter conversion and dark matter interactions.

Contribution

It reviews how muonium spectroscopy enables high-precision tests of fundamental physics and searches for new phenomena.

Findings

Measurement of hyperfine structure transitions for muon magnetic moment

Determination of muon mass via 1s-2s transition

Potential for testing antimatter and dark matter hypotheses

Abstract

The muonium atom is the purely leptonic bound state of a positive muon and an electron. It has a lifetime of 2.2 $\mu$s. The absence of any known internal structure provides for precision experiments to test fundamental physics theories and to determine accurate values of fundamental constants. In particular groun dstate hyperfine structure transitions can be measured by microwave spectroscopy to deliver the muon magnetic moment. The frequency of the 1s-2s transition in the hydrogen-like atom can be determined with laser spectroscopy to obtain the muon mass. With such measurements fundamental physical interactions, in particular Quantum Electrodynamics, can also be tested at highest precision. The results are important input parameters for experiments on the muon magnetic anomaly. The simplicity of the atom enables further precise experiments, such as a search for muonium-antimuonium conversion for testing charged lepton number conservation and searches for possible antigravity of muons and dark matter.