International Conference on Precision Physics of Simple Atomic Systems

Session

Session 2

18 May 2026, 11:00

Festsaal (ÖAW)

66. Progress in the calculation of order $\alpha^7$ radiative-recoil corrections to the energy levels of muonium and positronium

Gregory Adkins

18/05/2026, 11:00

Talk

Muonium and positronium, the $e^-\mu^+$ and $e^-e^+$ bound systems, are described almost completely within quantum electrodynamics. Their energy levels can be calculated to high precision, and these systems are also subject to high precision measurements. Recent developments include intense experimental work on muonium by the MuSEUM collaboration at J-PARC and the MuMASS collaboration at...

35. Precision continuous-wave spectroscopy of the 1S–2S transition in positronium and muonium

Edward Thorpe-Woods (ETH Zurich (CH))

18/05/2026, 11:30

Talk

Positronium and muonium, as purely leptonic atoms without internal structure, provide ideal systems for precision tests of quantum electrodynamics (QED) and searches for new physics [1].

We report a new measurement of the positronium $1^3S_1 \to 2^3S_1$ transition frequency using two-photon continuous-wave laser spectroscopy, $\nu = 1233607224.1(6.0)\ \mathrm{MHz}$ [2].
Our result agrees...

58. Precise Spectroscopy of Muonium Hyperfine Structure in High Magnetic Field

Shoichiro Nishimura (KEK IMSS)

18/05/2026, 12:00

Talk

Muonium is a bound state of a positive muon and an electron. Precise measurements of the muonium hyperfine structure (HFS) provide a stringent test of quantum electrodynamics (QED), whose theoretical predictions are calculated with extremely high precision [1]. In the field of precision muon physics, there is ongoing discussion regarding the hadronic vacuum polarization contribution to the...

7. Feasibility of Low-Energy True Muonium via Near-Threshold Photoproduction

Ivo Schulthess (ETH Zurich)

18/05/2026, 12:20

Talk

True muonium (µ⁺µ⁻), the purely leptonic bound state of a muon and an antimuon, is a unique atomic system that has not yet been observed experimentally. Together with positronium (e⁺e⁻) and muonium (µ⁺e⁻), it provides a clean laboratory for tests of bound-state quantum electrodynamics, while uniquely probing a regime characterized by a large reduced mass, extreme compactness, and short...