B-->Kl+l- with four generations: Rates and CP violation.

Abstract

In the standard model with three generations the branching ratios for B\ensuremath{\rightarrow}${\mathrm{Kl}}^{+}$${l}^{\mathrm{\ensuremath{-}}}$+X (B\ensuremath{\rightarrow}${\mathrm{Kl}}^{+}$${l}^{\mathrm{\ensuremath{-}}}$) are 1.9\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$ (0.9\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$) and 2.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$ (1.2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$) for ${m}_{t}$=40 and 80 GeV, respectively, with very little uncertainty, and the maximal CP-violation asymmetry is of the order of 1.5%. As demonstrated here in the standard model with four generations, these results may change drastically with a possibility of an increase by more than an order of magnitude in rates and CP-violation asymmetries. The uncertainty is now large for both quantities.