PRODUCTION OF HEAVY QUARKS CLOSE TO THRESHOLD

We calculate production by vector and axial vector currents of heavy q uark pairs (c (c) over bar, b (b) over bar, t (t) over bar) close to t hreshold. We take into account strong interaction contributions (inclu ding radiative corrections and leading nonperturbative effects) by usi ng the Fermi-Watson final-state interaction theorem. We use the result s obtained to compare with experiment for open production of c (c) ove r bar b (b) over bar near threshold, and to give a reliable estimate o f the so-called ''threshold effects'' contribution to vector and axial vector correlators, for t (t) over bar; i.e., the contribution of reg ions close to 4 m(t)(2) to II(t), for small values of t (0 < t less th an or similar to M(Z)(2)).