$W^{+}-H^{+}$ Interference and Partial Width Asymmetry in Top and Antitop Decays

Abstract

We re-examine the question of a possible difference in the partial decay widths of $t$ and $\overline{t}$, induced by an intermediate scalar boson $H^{+}$ with $CP$-violating couplings. The interference of $W^{+}$ and $H^{+}$ exchanges is analysed by constructing the $2\times 2$ 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 $t\to b{l}^{+}{\nu }_l$ and $t\to bc\overline{s}$, which fulfil explicitly the constraints of $CPT$ invariance. These results are contrasted with those in previous work.

Comments: 14 pages, report PITHA 94/19