Quarkonium formation time in a model-independent approach

We use dispersion relations to reconstruct, in a model-independent way, the formation dynamics of heavy quarkonium from the experimental data on e(+)e(-)-->(Q) over bar Q annihilation. We extract a distribution of formation times with a mean value for the J/psi, [tau(J/psi)]=0.44 fm; and for the Y, [tau(Y)]=0.32 fm. The corresponding widths of these distributions are given by Delta tau(J/psi)=0.31 fm and Delta tau(Y)=0.28 fm. This information can be used as an input in modeling of heavy quarkonium production on nuclear targets. [S0556-2813(99)50710-3].