The $D^*D \pi$ and $B^*B\pi$ couplings from light-cone sum rules

TL;DR

This paper refines the calculation of the strong couplings $D^*D ext{pi}$ and $B^*B ext{pi}$ using light-cone sum rules, incorporating higher-order corrections and analytical expressions for the spectral density.

Contribution

It introduces an improved analytical form of the spectral density including radiative corrections, enabling more accurate sum rule calculations of heavy meson-pion couplings.

Findings

Predicted $g_{D^*D ext{pi}}=14.1^{+1.3}_{-1.2}$

Predicted $g_{B^*B ext{pi}}=30.0^{+2.6}_{-2.4}$

Results agree with experimental and lattice QCD data.

Abstract

We revisit the calculation of the strong couplings $D^*D\pi$ and $B^*B\pi$ 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 ${\cal O} (\alpha_s)$ 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 $g_{D^*D\pi}=14.1^{+1.3}_{-1.2}$ and $g_{B^*B\pi}=30.0^{+2.6}_{-2.4}$ 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.