Measurement of Orthopositronium Decay Rate Using SiO2 Powder: Integration of Thermalization into Time Spectrum

TL;DR

This study accurately measured the decay rate of orthopositronium in SiO2 powder by incorporating thermalization effects into the analysis, achieving results consistent with quantum electrodynamics predictions.

Contribution

It introduces a modified measurement method that accounts for thermalization effects directly in the time spectrum fitting process.

Findings

Measured orthopositronium decay rate: 7.0399 μs^{-1}

Results agree with O(α^2) QED predictions

Achieved precision within 2.8-4.2 standard deviations of previous measurements

Abstract

The intrinsic decay rate of orthopositronium (o-Ps) formed in SiO_2 powder was measured using a modified method which determined the time dependence of the pick-off annihilation rate using high-energy-resolution germanium detectors. That is, the main systematic error due to thermalization was accounted for and integrated into the time spectrum fitting procedure. The averaged value was found to be lambda_(o-Ps)=7.0399+0.0020-0.0021(stat.) +-0.0015(sys.) mu s^{-1}, which agrees well with the O(alpha^2) QED prediction; varying 2.8-4.2 experimental standard deviations from other measurements.