Two-loop QCD corrections to the heavy quark pair production cross section in e+e- annihilation near threshold

We present O(alpha(s)(2)) corrections to the cross section for e(+)e(-) --> gamma* --> Q (Q) over bar close to threshold. We assume that the energy of the reaction is such that both the perturbative expansion in the strong coupling constant ct, and expansion in the velocity beta of the heavy quarks can be used. We obtain terms O(alpha(s)(2)/beta(2), alpha(s)(2)/beta, alpha(s)(2)) in the relative correction. We demonstrate how an expansion of Feynman diagrams in the threshold region is constructed. We obtain a matching relation between the vector current in full QCD and in nonrelativistic QCD.