  Charmonium formation via charm quark in-medium recombination in heavy ion
interactions at collider energies has the potential to probe some properties of
the medium by utilizing the sensitivity of the recombination process to the
momentum distribution of the quarks. We have examined the transverse momentum
spectra of J/Psi, characterized by <p_T^2>, which result from the formation
process in which the charm quark distributions are unchanged from their initial
production in a pQCD process. This is contrasted with the case in which the
charm quarks have completely come into thermal equilibrium with an expanding
medium whose properties are determined by the spectra of produced light
hadrons. We find that the resulting <p_T^2> of the formed J/Psi provide a
distinct signature of the underlying charm quark spectra, and that signature is
essentially independent of the detailed dynamics of the in-medium formation
reaction. In addition, both of these signatures are sufficiently separated from
the case in which no in-medium formation takes place. Finally, utilizing a
model for the fraction of J/Psi which originate from in-medium formation, we
predict the centrality behavior of these signatures.
