CORRECTION FACTORS FOR REACTIONS INVOLVING Q(Q)OVER-BAR ANNIHILATION OR PRODUCTION

In reactions with qq production or qq annihilation, initial- and final-state interactions give rise to large corrections to the lowest-order cross sections. We evaluate the correction factor first for low relative kinetic energies by studying the distortion of the relative wave function. We then follow the procedure of Schwinger to interpolate this result with the well-known perturbative QCD vertex correction factors at high energies, to obtain an explicit semiempirical correction factor applicable to the whole range of energies. The correction factor predicts an enhancement for qq in color-singlet states and a suppression for color-octet states, the effect increasing as the relative velocity decreases. Consequences on dilepton production in the quark-gluon plasma, the Drell-Yan process, and heavy quark production processes are discussed. © 1995 The American Physical Society.