We calculate the correction to $q\overline{q}\to t\overline{t}$ of order $\frac{g^2{m}_t^2}{M_W^2}$. This correction, proportional to the square of the Higgs-boson Yukawa coupling to the top quark, arises from loops of Higgs bosons and the scalar component of virtual vector bosons. The Yukawa correction to the total $t\overline{t}$ production cross section at the Fermilab Tevatron in the standard Higgs model is found to be much less than the theoretical uncertainty in the cross section. However, in a two-Higgs-doublet model, Yukawa couplings are generally enhanced. The Yukawa correction can increase the total $t\overline{t}$ production cross section in this model by as much as 20-35%, which is potentially observable at the Tevatron.

• Received 5 February 1993

DOI:https://doi.org/10.1103/PhysRevD.48.2054