Three loop top quark contributions to the ρ parameter Original Research Article

We present results for the three-loop top quark contributions to the ρ parameter in the limit of large top quark mass. The simultaneous dependence on the mass of the Higgs boson MH and the mass of the top quark mt is obtained from expansions in the range of MH around mt and in the limit MH⪢mt. In combination with the previous result for MH=0 the dependence of the ρ parameter on the leading Yukawa contributions, i.e., on mt and MH, is well under control for all mass values of practical importance. The effects lead to a shift in the W mass in the order of 5 MeV and are relevant for precision measurements at TESLA.