Precision Measurement of Orthopositronium Decay Rate Using SiO_2 Powder
Abstract
The intrinsic decay rate of orthopositronium formed in
Si
O
2
powder is measured using the direct
2γ
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
Si
O
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.)μ
s
−1
, which is consistent with previous measurements using
Si
O
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.