Positronium lifetime puzzle

by Andrzej CZARNECKI (Brookhaven National Laboratory)

Thursday 30 Sept 1999, 14:00 → 16:00 Europe/Zurich

TH Auditorium (CERN)

A major puzzle in bound-state QED is the discrepancy between measurements and theoretical predictions for the orthopositronium lifetime. On the basis of partial results, it has been speculated that anomalously large two-loop QED corrections might be responsible for this difference. Recently, we have computed the complete two-loop corrections to parapositronium lifetime. We find that the sum of long and short-distance effects is small, and conclude that the 'orthopositronium lifetime puzzle' will not likely be solved by large QED corrections. The method we developed can also be applied in QCD, e.g. to study quarkonium decays or top quark threshold production in gamma-gamma collisions.