W+-H+ interference and partial width asymmetry in top quark and top antiquark decays

We reexamine the question of a possible difference in the partial decay widths of t and bar t, induced by an intermediate scalar boson H+ with CP-violating couplings. The interference of W+ and H+ exchanges is analyzed by constructing the 2x2 propagator matrix of the W+-H+ system, and determining its absorptive part in terms of fermion loops. Results are obtained for the partial rate difference in the channels t→bl+νl and t→bc bar s, which fulfill explicitly the constraints of CPT invariance. These results are contrasted with those in previous work