Scattering of clusters in quantum calogero model

It is well known that scattering of particles in the Calogero model, which recently drew attention in connection with $c=1$ strings and integrable models in statistical mechanics, is reduced to two-particle collisions. It follows from Harish-Chandra and Gindikin–Karpelevich results, related to the harmonic analysis on simple Lie groups. Unfortunately their formulae don't work if particles form clusters in the asymptotics. We reformulate their results in a form which allows to apply them to this situation. The scattering of clusters is also factorizible, but depends on structures of constituents. In conclusion we discuss a similar problem in the deformed Calogero model related to quantum groups, which describes also interactions of excited states in the XXZ-model.