Gauge dependence of fermion mass renormalization schemes

We discuss the gauge dependence of fermion mass definition and physical result under the conventional on-shell mass renormalization scheme and the recently proposed pole mass renormalization scheme in standard model. By the two-loop calculations of top quark's mass counterterm and the cross section of physical process $W^{-}W^{+}\to b\bar{b}$ we strictly prove that the on-shell mass renormalization scheme makes fermion mass definition and the physical result gauge dependent at the first time, while we don't find such gauge dependence in the pole mass renormalization scheme. Besides, our calculation also shows the difference of the physical result between the two mass renormalization schemes cannot be neglected at two-loop level.