Next-to-next-to-leading order matching of beauty-charmed meson Bc and B *c decay constants

We present the next-to-next-to-leading order (NNLO) quantum chromodynamics (QCD) corrections to the decay constants for both the pseudoscalar Bc meson and the vector B*(c) meson in the nonrelativistic QCD (NRQCD) effective theory. The explicit NNLO calculations prove that the B-c decay constant from the pseudoscalar current is identical with the B-c decay constant from the axial-vector current. The NNLO result for the vector decay constant of B-c(*) meson is novel. Combining this result with the latest extraction of the NRQCD long-distance matrix elements of B-c and B-c(*) meson, we calculate and show the theoretical predictions for the branching ratios of the leptonic decays B-c(+)/B(*)c(+) l(upsilon l)(+) with l(+) = (e(+) , mu(+) , tau(+) ). In addition, the novel anomalous dimension for the flavor-changing heavy quark vector current in the NRQCD effective theory is helpful to investigate the threshold behaviors of the two different heavy quarks.