Relations among Bc → J/ψ, ηc form factors

A bstract We analyze the form factors parametrizing B c → J/ψ, η matrix elements of operators in a generalized low-energy b semileptonic Hamiltonian. consider an expansion nonrelativistic QCD, classifying heavy quark spin symmetry breaking terms and expressing universal functions selected kinematical range. Using as input lattice QCD results for J/ψ element SM operator, we obtain information on other factors. The extrapolation to full range is also presented.