Discussion about the orthopositronium decay rate and analysis of some $O({\alpha }^2)$ contributions

Abstract

I consider the problem of the evaluation of the orthopositronium decay rate, including second order radiative corrections. I present a brief theoretical discussion of this problem and a review of the results available in literature, and, then, I analyze some $O({\alpha }^2)$ annihilation-type contributions, recently computed.

Extended version of the talk given at the International Workshop "HADRONIC ATOMS AND POSITRONIUM IN THE STANDARD MODEL", DUBNA, 26-31 MAY 1998 11 pages, latex, 4 figures