Complete two-loop electroweak fermionic corrections to the effective leptonic weak mixing angle sin2θefflept and indirect determination of the Higgs boson mass -: art. no. 201805

We present a complete calculation of the contributions to the effective leptonic weak mixing angle, sin(2)theta(eff)(lept), 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 M-H of the standard model Higgs boson. The size of the corrections with respect to known partial results varies between -4x10(-5) and -8x10(-5) for a realistic range of M-H from 100 to 300 GeV. This translates into a shift of the predicted (from sin(2)theta(eff)(lept) alone) central value of M-H 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.