Semiclassical approach to multiparticle production

We use singular euclidean solutions to calculate semiclassically the cross sections for the production of some coherent multiparticle states in quantum field theories. In the weakly coupled λφ4 theory, at low energies E<>E0 for multiplicities n∝1/λ we find that the cross section approaches a constant magnitude of the form exp(-const./λ), controlled by the massless theory (m=0). We argue that similar high-energy limits, determined within the massless SU(2)xU(1) gauge theory with scalars and pure SU(3) gauge theory, apply to some coherent multi-W events in the electroweak theory and multiparticle events in QCD, respectively. (orig.)