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 − → ¯ QQ annihilation. We extract a distribution of formation times with a mean value for the J/ , = 0.44 fm; and for the �, = 0.32 fm. The corresponding widths of these distributions are given by �� J/ = 0.31 fm and ��� = 0.28 fm. This information can be used as an input in modeling of heavy quarkonium production on nuclear targets.