Nature Physics· 2026Q1
Generation of a high-intensity, superthermal muonium beam for gravity and laser spectroscopy experiments
- 1citations
- Q1SCImago
- 2026year
Short summary
Researchers generated a high-brightness, superthermal muonium beam from superfluid helium, enabling precision gravity measurements and sub-kilohertz laser spectroscopy.
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Key points
- A high-brightness, superthermal muonium beam was generated from superfluid helium.
- The beam exhibits a narrow velocity distribution, similar in yield to existing diffuse sources.
- Enables percent-level measurement of muonium's gravitational acceleration via interferometry.
- Opens possibilities for sub-kilohertz 1S-2S spectroscopy to determine muon mass and test QED.
AI-generated from the title and abstract; the full text is not read.
Abstract
Abstract The universality of free fall, a cornerstone of Einstein’s theory of gravity, has so far only been tested with neutral composite states of first-generation standard model particles, such as atoms, neutrons and antihydrogen. Muonium, the bound state of a positively charged anti-muon and an electron, offers the possibility to probe gravity in the absence of the strong interaction with second-generation standard model particles. However, the short muon lifetime and the existing diffuse thermal muonium sources rendered such measurements unfeasible. Here we report the generation of a high-brightness muonium beam, which we extract from a thin layer of superfluid helium. The mean longitudinal velocity and narrow spread of the velocity distribution indicate a superthermal beam, and yields are similar to the highest-intensity diffuse sources. This beam is expected to enable muonium interferometry and a per-cent-level measurement of its gravitational acceleration. In addition, its unprecedented brightness opens the way to sub-kilohertz 1S–2S spectroscopy, enabling the precise determination of the muon mass and stringent tests of bound-state quantum electrodynamics.
The authors' abstract, as published at the source. Nature Physics, 2026 · DOI ↗
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Field: Atomic and Molecular Physics, and Optics
Atomic and Molecular Physics, and OpticsPhysics and Astronomy