Precision measurement of the Lamb shift in Muonium

TL;DR

This paper presents a highly precise measurement of the Lamb shift in Muonium using microwave spectroscopy, aligning with theoretical predictions and constraining new physics beyond the Standard Model.

Contribution

It provides the most accurate experimental value of the Muonium Lamb shift to date, improving the precision by an order of magnitude over previous measurements.

Findings

Measurement matches theoretical predictions within one standard deviation.

Sets limits on CPT violation in the muonic sector.

Constrains new physics models related to the muon g-2 anomaly.

Abstract

We report a new measurement of the $n=2$ Lamb shift in Muonium using microwave spectroscopy. Our result of $1047.2(2.3)_\textrm{stat}(1.1)_\textrm{syst}$ MHz comprises an order of magnitude improvement upon the previous best measurement. This value matches the theoretical calculation within one standard deviation allowing us to set limits on CPT violation in the muonic sector, as well as on new physics coupled to muons and electrons which could provide an explanation of the muon $g-2$ anomaly.