The B_c meson and its scalar cousin with the QCD sum rules

In this work, we use optical theorem to calculate the next-to-leading order corrections to the spectral densities directly in the QCD sum rules for the pseudoscalar and scalar B_c mesons. We take the experimental data as guides to perform updated analysis, and obtain the masses and decay constants, therefore the leptonic decay widths, which can be confronted to the experimental data in the future.