Nonperturbative three-point functions of the O(N) sigma model in the 1/N   expansion at NLO
  We present a calculation of the three-point functions of the O(N)-symmetric sigma model. The calculation is done nonperturbatively by means of a higher-order 1/N expansion combined with a tachyonic regularization which we proposed in previous publications. We use the results for calculating the standard model process ff -> H -> WW nonperturbatively in the quartic coupling of the scalar sector. 
A. Ghinculov and T. Binoth