A Theoretical Prediction for Exclusive Decays $B \rightarrow K(K^*) \eta_c$

The decay rates for the exclusive B decays $B \rightarrow K \eta_c$ and $B \rightarrow K^* \eta_c$ are calculated in the context of the heavy quark effective theory. We obtain $\Gamma (B \rightarrow K \eta_c )/\Gamma (B\rightarrow K\psi )=1.6 \pm 0.2$ and $\Gamma (B\rightarrow K^*\eta_c)/\Gamma (B \rightarrow K^*\psi )=0.39 \pm 0.04$. These results lead to estimates $BR(B \rightarrow K \eta_c)=(0.11 \pm 0.02) \%$ and $BR(B \rightarrow K^* \eta_c)= (0.05 \pm 0.01) \%$ if we use the central current experimental values for $B\rightarrow (K,K^*)\psi$ branching ratios.