Heavy-quarkonium hadron cross section in QCD at leading twist

21 pages, 4 figures, REVTeX4. Discussion of the scale dependence extendedWe compute the total cross section of a heavy quarkonium on a hadron target in leading twist QCD, including target mass corrections. Our method relies on the analytical continuation of the operator product expansion of the scattering amplitude, obtained long ago by Bhanot and Peskin. The cross section has a simple partonic form, which allows us to investigate the phenomenology of J/psi and Upsilon dissociation by both pions and protons