  The enhancement of pions and kaons observed at small transverse momenta in
ultra-relativistic heavy-ion collisions may at least partly reflect critical
scattering expected to occur in the neighborhood of a second order phase
transition. Kinetic equations in the relaxation time approximation are proposed
for the time evolution of the quark distribution function into that of the
pions. Relaxation times for thermalization and hadronization processes are
functions of momenta and approach zero in the limit p->0, a consequence of
criticality at the phase transition. Data can be reproduced for suitably chosen
parameters.

High Energy Physics - Phenomenology