Precision measurement of orthopositronium decay rate using SiO2 powder

Abstract The intrinsic decay rate of orthopositronium formed in SiO 2 powder is measured using the direct 2 γ 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 SiO 2 powder are used with consistent findings. The intrinsic decay rate of orthopositronium is found to be 7.0396±0.0012(stat)±0.0011(sys) μs −1 , which is consistent with previous measurements using SiO 2 powder with about twice the accuracy. Results agree well with a recent O( α 2 ) QED prediction, varying 3.8–5.6 experimental standard deviations from other measurements.