Hard-soft factorization in B_c--> psi pi decay

The width of $B_c^{+}\to \psi {\pi }^{+}$ decay is calculated in the framework of factorization of a hard gluon exchange and a soft binding of quarks in the heavy quarkonium, so that $\mathrm{B}\mathrm{R}(B_c^{+}\to \psi {\pi }^{+})=2.0\pm 0.5$ %.