Exclusive and Semi-Inclusive B Decays Based on \hspace{0.3cm} b   $\rightarrow$ s \hspace{0.01cm}$\eta_c$ \hspace{0.3cm} Transition
  We calculate the semi-inclusive processes B $\rightarrow X_{s} \eta_c$ and relate it to B $\rightarrow X_{s} \psi$ in next to leading order QCD, and show how it can be used to determine an accurate value of $f_{\eta_{c}}$. The exclusive modes B $\rightarrow$ K$\eta_c$ and B $\rightarrow$ K$\psi$ also yield similar results, whereas B $\rightarrow$ K$^*\eta_c$ and B $\rightarrow$ K$^*\psi$ can provide valuable information on hadronic form factors. We also estimate the branching ratios and the ratios of exclusive to inclusive decay modes dominated by $b \rightarrow s\e$. 
N. G. Deshpande and Josip Trampetic