Radiative corrections due to enhanced Yukawa couplings

In models with more than one Higgs doublet, a 40-GeV t quark can have an extremely large Yukawa coupling. This coupling can influence, through radiative corrections, precision measurements of the W-to-Z mass ratio and the lepton-pair polarization asymmetry in Z decays. We calculate the size of these corrections, and find that they can only be experimentally significant if the enhancement of the coupling is greater than 5. The corrections are unique in that they involve neither drastically new physics nor very heavy particles.

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