We analyze the form factors parametrizing the Bc→J/ψ,ηc matrix elements of the operators in a generalized low-energy b→c semileptonic Hamiltonian. We consider an expansion in nonrelativistic QCD, classifying the heavy quark spin symmetry breaking terms and expressing the form factors in terms of universal functions in a selected kinematical range. Using as an input the lattice QCD results for the Bc→J/ψ matrix element of the SM operator, we obtain information on other form factors. The extrapolation to the full kinematical range is also presented.
@article{arxiv.2205.08933,
title = {Relations among $B_c \to J/\psi, \eta_c$ form factors},
author = {P. Colangelo and F. De Fazio and F. Loparco and N. Losacco and M. Novoa-Brunet},
journal= {arXiv preprint arXiv:2205.08933},
year = {2022}
}