The $D^{\ast }D\pi$ and $B^{\ast }B\pi$ couplings from light-cone sum rules

Abstract

We revisit the calculation of the strong couplings $D^{\ast }D\pi$ and $B^{\ast }B\pi$ from the QCD light-cone sum rules using the pion light-cone distribution amplitudes. The accuracy of the correlation function, calculated from the operator product expansion near the light-cone, is upgraded by taking into account the gluon radiative corrections to the twist-3 terms. The double spectral density of the correlation function, including the twist-2, 3 terms at $\mathcal{O}({\alpha }_s)$ and the twist-4 LO terms, is presented in an analytical form for the first time. This form allows us to use various versions of the quark-hadron duality regions in the double dispersion relation underlying the sum rules. We predict $g_{D^{\ast }D\pi }=14.1_{-1.2}^{+1.3}$ and $g_{B^{\ast }B\pi }=30.0_{-2.4}^{+2.6}$ when the decay constants of heavy mesons entering the light-cone sum rule are taken from lattice QCD results. We compare our results with the experimental value for the charmed meson coupling and with the lattice QCD calculations.

Comments: 41 pages, 3 figures, a few comments added, the version published in JHEP