Fourth-generation effect on CP violation in Bd hadronic decays.

Abstract

Du, Dunietz, and Wu examined $\mathrm{CP}$ violation in partial-decay-rate asymmetries of neutral $b$-flavored mesons in the standard Kobayashi-Maskawa (KM) model. We calculate in the four-generation model the same $\mathrm{CP}$ asymmetry in ${B}_{d}$ hadronic decays in light of the large ${B}_{d}\ensuremath{-}{\overline{B}}_{d}$ mixing obtained by the ARGUS and CLEO Collaborations. The general 4\ifmmode\times\else\texttimes\fi{}4 KM matrix proposed by Botella and Chau is used. The effect of the fourth generation on asymmetry is found to be sizable for various mixings of the fourth with the preceding three generations, changing signs of the asymmetry in the modes $\overline{b}\ensuremath{\rightarrow}\overline{u}\mathrm{ud}$ and $\overline{b}\ensuremath{\rightarrow}\overline{c}c\overline{d}$, and enhancing magnitudes in the modes $\overline{b}\ensuremath{\rightarrow}\overline{u}c\overline{d}$ and $\overline{b}\ensuremath{\rightarrow}\overline{c}u\overline{d}$ from their standard-model predictions.