CONTRIBUTION OF LIGHT-BY-LIGHT SCATTERING TO THE ORDERS O(M-ALPHA(8)) AND O(M-ALPHA-IN-8 ALPHA) ORTHOPOSITRONIUM DECAY-RATE

The gauge invariant contribution of the six radiatively corrected light-by-light scattering processes to the decay rate of orthopositronium into three photons is calculated. The infrared-safe Yennie gauge is used for the loop photons. The relative order of α2 part of our result, 9.0074(9)(α2/π2)ΓLO, makes a 0.000350 μs-1 contribution to the decay rate, thus reducing slightly the apparent discrepancy between the theoretical and experimental results. ΓLO is the lowest-order decay rate. The analytically obtained relative order α2ln α part of our result, -α2ln(1/α)ΓLO, is in agreement with earlier evaluations. © 1995 The American Physical Society.