First test of O(α2)O(α2) correction of the orthopositronium decay rate

Positronium is an ideal system for the research of the bound state QED. New precise measurement of orthopositronium decay rate has been performed with an accuracy of 150 ppm. This result is consistent with the last three results and also the 2nd order correction. The result combined with the last three is 7.0401±0.0007μs−1 (100 ppm), which is consistent with the 2nd order correction and differs from the 1st order calculation by 2.6σ. It is the first test to validate the 2nd order correction.