CP violation in $t\rightarrow W^+b$ decays in two-Higgs doublet model

Abstract

Due to the large mass of top quark, CP violation in the top-quark decay is sensitive to the interactions medi- ated by Higgs bosons. We consider CP violation in t → W + b decay by calculating consistently in unitary gauge the CP- violating up-down asymmetry of the leptons from W boson decays in t → W + b, defined by Grzadkowski and Gunion, in the two-Higgs doublet model with CP-violating neutral sector. The asymmetry is shown to be at most of the order of (1 −4) ×10 −4 for tan β =1 .0, where tan β is the ratio of vacuum expectation values for the two neutral Higgs bosons.