Bosonic corrections to the effective weak mixing angle at O(α2)

We present the complete bosonic contributions to the effective weak mixing angle, sin2θefflept, at the two-loop level in the electroweak interactions. We find their size to be about three times smaller than inferred from simple estimates from lower orders. In particular, for a Higgs boson mass, MH, of 100 GeV they amount to 4×10−6, and drop down by about an order of magnitude for MH=200GeV. We estimate the intrinsic error of the theory prediction of sin2θefflept to be 4.7×10−5.