  Wet granular materials are characterized by a defined bond energy in their
particle interaction such that breaking a bond implies an irreversible loss of
a fixed amount of energy. Associated with the bond energy is a nonequilibrium
transition, setting in as the granular temperature falls below the bond energy.
The subsequent aggregation of particles into clusters is shown to be a
self-similar growth process with a cluster size distribution that obeys
scaling. In the early phase of aggregation the clusters are fractals with
D_f=2, for later times we observe gelation. We use simple scaling arguments to
derive the temperature decay in the early and late stages of cooling and verify
our results with event-driven simulations.
