Complete two-loop electroweak fermionic corrections to the effective leptonic weak mixing angle sin(2θlepteff and indirect determination of the Higgs boson mass.

Abstract

We present a complete calculation of the contributions to the effective leptonic weak mixing angle, sin2, generated by closed fermion loops at the two-loop level of the electroweak interactions. This quantity is the source of the most stringent bound on the mass MH of the standard model Higgs boson. The size of the corrections with respect to known partial results varies between –4×10–5 and –8×10–5 for a realistic range of MH from 100 to 300 GeV. This translates into a shift of the predicted (from sin2 alone) central value of MH by +19 GeV, to be compared with the shift induced by a recent change in the measured top quark mass which amounts to +36 GeV.