Study of Form Factors and Observables in B_c^- rightarrow bar{D}^{(*)0}ell^-bar{ν}_{ell} and B_c^- rightarrow D^{(*)-}ell^+ell^- decays

We investigate the decays $B_c^- \rightarrow \bar{D}^{(*)0}\ell^-\bar{\nu}_{\ell}$ and $B_c^- \rightarrow D^{(*)-}\ell^+\ell^-$ within the Standard Model (SM), employing perturbative QCD (pQCD) form factors that are sensitive to the wave functions of $B_c$ and $D^{(*)}$ mesons. Using lattice QCD inputs for $B \to D^{(*)}$ and $B_c \to D$ transitions, we extract the shape parameters of the meson wave functions and estimate the $q^2$-dependence of $B_c \to D^*$ form factors via heavy quark spin symmetry. We present predictions for branching fractions, lepton flavor violating observables, and perform a detailed angular analysis of the cascade decay $B_{c}^{-} \to D^{*-}(\to D^{0}\pi^{-}) \ell^+\ell^-$, providing SM expectations for several angular observables.