Constraints on the mass and mixing of the fourth generation quark from directCPviolationε′/εand rareKdecays

Abstract

We investigate the ⑀Ј/⑀ for K→ in a sequential fourth generation model. By giving the basic formulas for ⑀Ј/⑀ in this model, we analyze the numerical results which are dependent on m t Ј and the imaginary part of the fourth CKM factor, ImV t Ј s * V t Ј d ͑or V t Ј s * V t Ј d and the fourth generation CKM matrix phase ). We find that, unlike the SM, when taking the central values of all parameters for ⑀Ј/⑀, the values of ⑀Ј/⑀ can easily fit to the current experimental data for all values of hadronic matrix elements estimated from various approaches. Also, we show that the experimental values of ⑀Ј/⑀ and rare K decays can provide a strong constraint on both mass and mixing of the fourth generation quark. When taking the values of hadronic matrix elements from the lattice or 1/N expansion calculations, a large region of the up-type quark mass m t Ј is excluded.

Bounds on the mass of theb′quark, reexamined

“…Hence, the b ′ can not decay to a top quark. Furthermore, while some recent studies [7,8] have constrained the Cabibbo-Kobayashi-Maskawa (CKM) elements of the fourth generation, they do not influence our results. Nevertheless we will take into account the 2σ bound…”

Waiting for precise measurements ofK+→π+νν¯andKLBuras1, Uhlig2, Schwab3 2008Rev. Mod. Phys.10501160View full textAdd to dashboardCite

“…For completeness, we describe them here. , 1998;Huang et al, 2001;Yanir, 2002͒ due to three additional mixing angles and two additional complex phases, Br͑K L → 0 ͒ can be enhanced by one to two orders of magnitude with respect to SM expectations and also Br͑K + → + ͒ can be significantly enhanced. Unfortunately, due to many free parameters, the four generation models are not very predictive.…”