BC_NPI module for the analysis of Bc -> J/psi +n pi and Bc -> B_s +n pi   decays within the EvtGen package
  The module for the generation of $B_c$ meson decays into $J/\psi + n\pi$ and $B_s^{(*)} + n\pi$ ($n\le 4$) is implemented into EvtGen program package. The decay amplitudes are calculated in the frame work of factorization model. Within this approach the decay can be represented as $B_c$ decay into $J/\psi (B_s)+W^*$ followed by the virtual $W^*$-boson decay into the final set of $\pi$-mesons. The described calculation technique allows to adopt the parameters of $W^*\to n\pi$ transition from the analysis of $\tau$ decay into $\nu_\tau+n\pi$. Comparison with available theoretical predictions is performed. 
A.V. Berezhnoy, A. K. Likhoded and A. V. Luchinsky
hep-ph