  Early local equilibration of a hot medium created in high-energy heavy ion
collisions has been one of the long standing issues in hadron physics. The
glasma model predicts that the medium initially has a large amount of
high-momentum gluons but few quarks. We develop a phenomenological model based
on collinear splitting and recombination of quarks and gluons for a simplified
description of thermalization and chemical equilibration. We find that both
could be achieved in a short time but chemical equilibration is slower than
thermalization.
