Precision measurements of positronium decay rate and energy level

TL;DR

This paper reports highly precise measurements of positronium decay rate and hyperfine splitting, validating second-order QED corrections and proposing improved methods to resolve existing discrepancies with theoretical predictions.

Contribution

It provides the first validation of second-order QED corrections for positronium decay and introduces new measurement techniques to address previous systematic uncertainties.

Findings

Decay rate measured with 150 ppm accuracy

Validation of second-order QED correction

Identification of potential sources for HFS discrepancy

Abstract

Positronium is an ideal system for the research of the bound state QED. New precise measurement of orthopositronium decay rate has been performed with an accuracy of 150 ppm, and the result combined with the last three is 7.0401 +- 0.0007 mu s^-1. It is the first result to validate the 2nd order correction. The Hyper Fine Splitting of positronium is sensitive to the higher order corrections of the QED prediction and also to the new physics beyond Standard Model via the quantum oscillation into virtual photon. The discrepancy of 3.5 sigma is found recently between the measured values and the QED prediction (O(alpha^3)). It might be due to the contribution of the new physics or the systematic problems in the previous measurements: (non-thermalized Ps and non-uniformity of the magnetic field). We propose new methods to measure HFS precisely without the these uncertainties.