The Decay Rate Asymmetry of the Top Quark

The asymmetries Ak ≡ [Γ(t → Wdk)−Γ(t̄ → Wd̄k)]/[Γ(t → Wdk)+Γ(t̄ → Wd̄k)] 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 Ab can be substantial, O(αQCD), provided the CP-violating phase of gluino-top-stop couplings is not suppressed. Within the SSM Ab is generated by the vertex corrections. CERN-TH.6941/93 July 1993 E-mail: bohdang@cernvm. Address after 1 October 1993: Institute for Theoretical Physics, University of Warsaw, Hoża 69, PL-00681 Warsaw, Poland. E-mail: keung@fnal. Address after 1 August 1993: Physics Department, M/C 273 University of Illinois at Chicago, IL 60607– 7059, USA.