Two-loop large Higgs mass correction to the ro-parameter

Abstract

The two-loop correction to the ro-parameter in the limit of the large Higgs mass is calculated. Numerically it is found that the two-loop contribution is equal in magnitude, but of opposite sign to the one-loop correction if the Higgs mass is about 137 times the vector boson mass. The calculation suggest a breakdown of perturbation theory if the Higgs mass is larger than 3 TeV. There is no direct correspondence between our results and the poles at n = 3 of the simple non-linear -model at the two-loop level.