$B^- \to K^- \chi_{c0}$ decay from charmed meson rescattering
  We study the process $B^- \to K^- \chi_{c0}$ considering intermediate charmed meson rescattering effects. For this decay mode the naive factorization ansatz would predict a vanishing amplitude. We estimate contributions from the $D^{(*)}_{s} D^{(*)}\to K^- \chi_{c0}$ rescattering amplitudes, and compare the result with recent experimental measurements. We find that rescattering effects are able to produce a large branching ratio consistent with measurements by Belle Collaboration. We also consider rescattering effects in $B^- \to K^- J/\psi$, arguing that they play a similar role in producing a large branching fraction for this colour-suppressed decay mode. 
P. Colangelo, F. De Fazio and T.N. Pham