CP-Violations and Effects of 4th Generation in B Meson Nonleptonic Decays : Particles and Fields

概要

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We investigate the effects of CP-violation in nonleptonic decays of neutral B mesons (B_d, B_s) in the Kobayashi-Maskawa model through quark exchange and W emission-diagrams in terms of the Wolfenstein matrix for three and four generations, using the new data of mixing parameter x_d=0.70 ±0.13, derived from the ARGUS and CLEO measurements, and those on the branching ratios for B_d decays. We obtain the results that the CP-violating asymmetries for B_d→D^+D^-, π^+π^- and K^+K^- reach the order of 40% and the number of bb^^- quark pairs needed to detect the asymmetry is 10^6-10^8 at 3σ level, and the asymmetries for B_s→D^^-^0π^0, D^-π^+, D^0π^0 and D^+π^- reach the order of 20% and the number of bb^^- pairs is order of 10^8. Therefore, we may conclude that the CP-violation for these decay modes is possibly observable at the present stage. The effects of 4th generation quarks on CP-violation prove to be quite small except for the mode b^^-→c^^-cs^^- among the eight "tree-diagram" decay modes studied here. The reason for such an effect of the 4th generation is due to the fact that a phase of box diagram amplitude is already saturated by the three generations.
理論物理学刊行会の論文
1990-02-25