ar X iv : h ep - p h / 98 05 45 6 v 1 2 6 M ay 1 99 8 Polarization in B̄ c →

We study the polarization of the J/ψ meson of the B̄c → J/ψ μ ν̄μ decay process, followed by J/ψ → μμ, with the help of the heavy-quark spin symmetry formalism (HQSS) of Jenkins et al. [1] We adapt the ISGW wave function. Due to the clean signature of the decay mode, measurements of the polarization of the J/ψ meson can play a special role in extracting |Vcb|, the quark mixing-matrix element. We compare the results with the predictions of other quark models.