Second order QCD corrections to the forward-backward asymmetry in e⁺e^- - collisions

Abstract

We will present the result of an analytical calculation of the second order contribution to the forward-backward asymmetry A_FB^H and the shape constant a^H for heavy flavour production in e⁺e^--collisions. The calculation has been carried out by assuming that the quark mass is equal to zero. This is a reasonable approximation for the exact second order correction for charm and bottom quark production at LEP energies but not for top production at future linear colliders. Our result for A_FB^H is a factor 2.6 (charm) and 4.7 (bottom) larger than obtained by a numerical calculation performed earlier in the literature. We study the effect of the second order corrections on the above parameters including their dependence on the renormalization scale. Further we make a comparison between the fixed pole mass and the running mass approach.