The orthopositronium lifetime puzzle and its final solution

The ortho-positronium (o-Ps), which consists of an electron and positron, is a pure lepton bound system. The o-Ps lifetime can be calculated accurately by quantum electrodynamics, but there is a long-standing discrepancy between the theoretical calculations and the experimental results. Theoretical and experimental physicists have worked hard for a long time to solve the problem, and recently finally solved this lifetime puzzle. The authors briefly outline the discrepancy between the theoretical calculations of the o-Ps annihilation decay rate and some of the experimental measurements, as well as recent developments of experimental techniques, and its final solution. In particular, the final results of the Tokyo and michigan groups are discussed