Precision Measurement of Orthopositronium Decay Rate Using SiO_2 Powder

TL;DR

This study precisely measures the decay rate of orthopositronium in SiO2 powder using advanced detection methods, achieving higher accuracy and confirming consistency with theoretical QED predictions.

Contribution

It introduces a direct 2γ correction method with high-resolution detectors to accurately determine orthopositronium decay rates in SiO2 powder, improving measurement precision.

Findings

Decay rate measured as 7.0396 μs^{-1} with high precision.

Results align with recent QED predictions within experimental uncertainties.

Consistent findings across different SiO2 powders.

Abstract

The intrinsic decay rate of orthopositronium formed in ${\rm SiO_2}$ powder is measured using the direct $2\gamma$ correction method such that the time dependence of the pick-off annihilation rate is precisely determined using high energy-resolution germanium detectors. As a systematic test, two different types of ${\rm SiO_2}$ powder are used with consistent findings. The intrinsic decay rate of orthopositronium is found to be $7.0396\pm0.0012 (stat.)\pm0.0011 (sys.)\mu s^{-1}$, which is consistent with previous measurements using ${\rm SiO_2}$ powder with about twice the accuracy. Results agree well with a recent $O(\alpha^2)$ QED prediction, varying $3.8-5.6$ experimental standard deviations from other measurements.