The Decay Rate Asymmetry of the Top Quark

Abstract

The asymmetries ${\cal A}_k \equiv [Γ(\twddec) -Γ(\tbwddec)] /[Γ(\twddec) + Γ(\tbwddec)]$ in the partial widths of the top quark decays are discussed within the Standard Model (SM), the Two-Higgs-Doublet Model (2HDM) and supersymmetric extensions of the SM (SSM). The leading contributions to these asymmetries in the SM and in the 2HDM are induced by the up-type quark self-energy diagrams and are found to be very small. However, in the SSM, the asymmetry ${\cal A}_b$ can be substantial, ${\cal O}(α_{QCD})$, provided the CP-violating phase of gluino-top-stop couplings is not suppressed. Within the SSM ${\cal A}_b$ is generated by the vertex corrections.