Quasi-Inclusive and Exclusive decays of $B$ to ${\eta }^{\mathrm{\prime }}$

We consider the effective Hamiltonian of four quark operators in the Standard Model in the exclusive and quasi-inclusive decays of the type $B\to K^{(*)} \eta^{\prime}$,$B\to \eta’ X_s$,where$X_s$ contains a single Kaon. Working in the factorization assumption we find that the four quark operators can account for the recently measured exclusive decays $B\to {\eta }^{\mathrm{\prime }}(\eta )K$ and $B\to K\pi$ for appropriate choice of form factors but cannot explain the large quasi-inclusive rate.