Positronium Hyperfine Splitting

TL;DR

This paper discusses new experimental approaches to measure the positronium hyperfine splitting with the aim of resolving discrepancies with QED predictions and exploring potential new physics beyond the Standard Model.

Contribution

It introduces two novel measurement methods for Ps-HFS, including a direct measurement without static magnetic field, and addresses systematic errors in previous experiments.

Findings

Initial prototype results without RF system

Development of a new direct measurement method

Ongoing data collection for direct transition observation

Abstract

Positronium is an ideal system for the research of QED in the bound state. The hyperfine splitting of positronium (Ps-HFS: about 203 GHz) is a good tool to test QED and also sensitive to new physics beyond the Standard Model. Previous experimental results show 3.9\,$\sigma$ (15 ppm) discrepancy from the QED $\mathrm{O}\left(\alpha ^3 \ln{1/\alpha}\right)$ prediction. We point out probable common systematic errors in all previous experiments. I measure the Ps-HFS in two different ways. (1) A prototype run without RF system is described first. (2) I explain a new direct Ps-HFS measurement without static magnetic field. The present status of the optimization studies and current design of the experiment are described. We are now taking data of a test experiment for the observation of the direct transition.