The Perturbative Onset of Multiparticle Production in Weak Interactions
  We use perturbation theory to estimate the energy scale beyond which multiparticle final states become a dominant feature of high energy weak interactions. Using estimates from a weak parton model and comparing two, three and four body final states we deduce that multiparticle states become important at energy scales in the range 10**7 - 10**9 GeV. 
D.A. Morris and R. Rosenfeld