New method of precise measurement of positronium hyperfine splitting

TL;DR

This paper discusses a new experimental approach to precisely measure positronium hyperfine splitting, aiming to resolve a significant discrepancy between theory and previous experiments, which could indicate new physics or systematic errors.

Contribution

It introduces a novel experimental method to measure positronium hyperfine splitting with improved accuracy, providing an independent check on existing discrepancies.

Findings

Prototype run achieved a measurement of 203.3804 GHz with 41 ppm precision.

The proposed experiment aims for ppm-level precision within a few years.

The study highlights potential implications for QED and beyond Standard Model physics.

Abstract

The ground state hyperfine splitting of positronium, $\Delta_{\mathrm{HFS}}$, is sensitive to high order corrections of QED. A new calculation up to $\mathrm{O}(\alpha ^3 \ln \alpha)$ has revealed a $3.9\sigma$ discrepancy between the QED prediction and the experimental results. This discrepancy might either be due to systematic problems in the previous experiments or to contributions beyond the Standard Model. We propose an experiment to measure $\Delta_{\mathrm{HFS}}$ employing new methods designed to remedy the systematic errors which may have affected the previous experiments. Our experiment will provide an independent check of the discrepancy. The prototype run has been finished and a result of $\Delta_{\mathrm{HFS}} = 203.380 4 \pm 0.008 4 \mathrm{GHz} (41 \mathrm{ppm})$ has been obtained. A measurement with a precision of O(ppm) is expected within a few years.