SOLUTION OF THE ORTHOPOSITRONIUM LIFETIME PUZZLE

Abstract
The intrinsic decay rate of orthopositronium formed in SiO 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.)μs-1, which is consistent with our previous measurements with about twice the accuracy. Results agree well with the O(α2) QED prediction, and also with a result reported very recently using nanoporous film.
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