Precision Muonium Spectroscopy

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.Comment: accepted for JPS

Small Magnetic Charges and Monopoles in Nonassociative Quantum Mechanics

“…If we directly apply hydrogen or muonium spectroscopy, with accuracies of ∆E/E ≈ 4.5 · 10 −15 [12] and about 10 −9 [32], respectively, we obtain weaker bounds: g proton ≤ 9.5 · 10 −8 g Dirac and g muon ≤ 4.5 · 10 −5 g Dirac . Acknowledgements: This work was supported in part by NSF grant PHY-1607414.…”

Intense beam of metastable Muonium

“…However, the puzzle is arguably nearing its solution [ 7 – 9 ]. To this day, precision experiments with M only utilized its ground-state [ 10 , 11 ]. The 1S–2S transition was measured by pulsed laser spectroscopy [ 12 , 13 ], putting tight bounds on the muon-electron charge ratio.…”

Current status and prospects of muonium spectroscopy at PSI

“…With a longer lifetime of 2196.9803( 22) ns [7], limited by the muon decay, and a larger mass, M is a more suitable candidate for precision spectroscopy experiments. Past M spectroscopy experiments were conducted between 1980 − 2000 at TRIUMF, RAL and LAMPF (see [8] for a recent review). As a result of the difficulty in obtaining a high flux of µ + , and the necessity to slow down the muons so that M can be formed efficiently, all past M spectroscopy experiments were essentially limited by statistics, or statistics-related systematic effects [8].…”