title: Order alpha(7)ln(1/alpha) contribution to positronium hyperfine splitting
abstract: The logarithmically enhanced alpha(7)ln(1/alpha) contribution to the hyperfine splitting of the positronium ground-state energy levels is calculated in the framework of dimensionally regularized nonrelativistic quantum electrodynamics. The correction is negative and amounts to about 1/3 of the leading logarithmic alpha(7)ln (2)(1/alpha) one. The discrepancy between the experimental measurements and the theoretical prediction is reduced.
authors: II. Institut fur Theoretische Physik, Universitat Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany.
authors: BA
authors: Kniehl
authors: AA
authors: Penin