  We use dispersion relations to reconstruct, in a model-independent way, the
formation dynamics of heavy quarkonium from the experimental data on e+ e-
annihilation to Q-bar Q. We extract a distribution of formation times with a
mean value for the J/psi, tau{J/psi} = 0.44 fm; and for the Upsilon,
tau{Upsilon} = 0.32 fm. The corresponding widths of these distributions are
given by Delta-tau{J/psi} = 0.31 fm and Delta-tau{Upsilon} = 0.28 fm. This
information can be used as an input in modeling of heavy quarkonium production
on nuclear targets.
