Solution of Orthopositronium lifetime Puzzle
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. The decay rate of orthopositronium is found to be
7.0396±0.0012(stat.)±0.0011(sys.)μ
s
−1
, which is consistent with our previous measurements with about twice the accuracy. Results agree well with the
O(
α
2
)
QED prediction, and also with a result reported very recently using nanoporous film.