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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 $J/ψ+ nπ$ and $B_s^{(*)} + nπ$ ($n\le 4$) 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 $J/ψ(B_s)+W^*$ followed by the virtual $W^*$-boson decay into the final set of $π$-mesons. The described calculation technique allows to adopt the parameters of $W^*\to nπ$ transition from the analysis of $τ$ decay into $ν_τ+nπ$. Comparison with available theoretical predictions is performed.