The ratios of B and D meson decay constants and also the double ratio (fBs/fBd)/(fDs/fDd) have been calculated using the variational method in conjunction with the relativistic Hamiltonian of the heavy meson in the framework of the statistical model. Using six different potentials of the potential model, we have obtained reliable results for them which are in good agreement with those of the lattice calculations.
Factorization of radiative leptonic D-meson decay with subleading power corrections