Prescription for finite oblique parameters S and U in extensions of the SM with mW != mZ cos thetaW

Meeting ID: 849 8854 1912
Meeting password: CFTP777

We consider extensions of the Standard Model with neutral scalars in multiplets of SU(2) larger than doublets. When those scalars acquire vacuum expectation values, the resulting masses of the gauge bosons W± and Z0 are not related by mW = mZ cos thetaW. In those extensions of the Standard Model the oblique parameters S and U, when computed at the one-loop level, turn out to be either gauge-dependent or divergent. We show that one may eliminate this problem by modifying the Feynman rules of the Standard Model for some vertices containing the Higgs boson; the modifying factors are equal to 1 in the limit mW = mZ cos thetaW. We give the result for S in a model with arbitrary numbers of scalar SU(2) triplets with weak hypercharges either 0 or 1.