Exponentiation of multiparticle amplitudes in scalar theories. II. Universality of the exponent.

It has been shown recently that the amplitude of the creation of n real scalar particles by one virtual boson near n–particle threshold exhibits exponential behavior at n ∼ 1/λ. We extend this result to the processes of multiparticle production at threshold by two virtual bosons. We find that both the tree–level amplitude and leading–n loop corrections have the same exponential behavior, with the common exponent for 1 → n and 2 → n processes, for various kinematics. This result strongly indicates that the exponent for multiparticle amplitudes is independent of the initial state and that there may exist a semiclassical approach to the study of multiparticle production.