Analytically integrated results for heavy fermion production in   two-photon collisions and a high precision $\alpha_s$ determination
  The cross section for massive fermion production in two-photon collisions was examined at next-to-leading order in QCD/QED for general photon helicity. The delta function (virtual+soft) part of the differential cross section was analytically integrated over the final state phase space. Series expansions for the complete differential and total cross sections were given up to tenth order in the parameter $\beta$. These were shown to be of practical use and revealed much structure. Accurate parametrizations of the total cross sections were given, valid up to higher energies. The above results were applied to top quark production in the region not too far above threshold. The cross section was shown to be quite sensitive to $\alpha_s$ in the appropriate energy region. 
B. Kamal and Z. Merebashvili