Role of B-c(+) - B-s,d(()()) (l)over-bar(vl) in the Standard Model and in the search for BSM signals

The decays B-c(+) -> B-a(l) over bar (vl) and B-c(+) -> B-a*(-> B-a gamma)(l) over bar (vl), with a = s, d and l = e, mu, are studied in the Standard Model (SM) and in the extension based on the low-energy Hamiltonian comprising the full set of dimension-6 semileptonic c -> s,d operators with left-handed neutrinos. Tests of mu/e universality are investigated using such modes. The heavy quark spin symmetry is applied to relate the relevant hadronic matrix elements and to exploit lattice QCD results on B-c form factors. Optimized observables are selected, and the pattern of their correlations is studied to identify the effects of the various operators in the extended low-energy Hamiltonian.