  We consider an effective kinetic description for quantum many-body systems,
which is not based on a weak-coupling or diluteness expansion. Instead, it
employs an expansion in the number of field components N of the underlying
scalar quantum field theory. Extending previous studies, we demonstrate that
the large-N kinetic theory at next-to-leading order is able to describe
important aspects of highly occupied systems, which are beyond standard
perturbative kinetic approaches. We analyze the underlying quasiparticle
dynamics by computing the effective scattering matrix elements analytically and
solve numerically the large-N kinetic equation for a highly occupied system far
from equilibrium. This allows us to compute the universal scaling form of the
distribution function at an infrared nonthermal fixed point within a kinetic
description and we compare to existing lattice field theory simulation results.
