2-LOOP CORRECTIONS TO THE ORTHOPOSITRONIUM AND PARAPOSITRONIUM DECAY-RATES DUE TO VACUUM POLARIZATION

We have calculated all O(alpha(2)) corrections to the orthopositronium and parapositronium decay rates due to vacuum polarization graphs. These contributions are independent of gauge and bound state formalism. Our results are +0.964 960(4) (alpha/pi)(2) for orthopositronium and $0.447 343 0(6) (alpha/pi)(2) for parapositronium relative to the lowest order rates. We also have an improved result for the one-loop one-photon-annihilation orthopositronium decay graph of -0.814 057 4(10) (alpha/pi) times the lowest order rate.