Study of form factors and observables in Bc⁻ → D̄( )0⁻ν̄ and Bc⁻ → D(∗)−ℓ+ℓ− decays

A bstract We investigate the decays Bc⁻ B c − → D̄( )0⁻ν̄ D ¯ ∗ 0 ℓ − ν ¯ ℓ and Bc⁻ B c − → D (∗)− ℓ + ℓ − 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 → D (∗) and B c → D transitions, we extract the shape parameters of the meson wave functions and estimate the q 2 -dependence of B c → 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 Bc⁻ B c − → D ∗− (→ D 0 π − ) ℓ + ℓ − , providing SM expectations for several angular observables.