The $K^\ast K\pi$ and $\rho\pi\pi$ couplings in QCD

Abstract

The light cone QCD sum rules are derived for the $K^\ast K\pi$ coupling $g_{K^\ast K\pi} $ and the $\rho\pi\pi$ coupling $g_{\rho\pi\pi}$. The contribution from the excited states and the continuum is subtracted cleanly through the double Borel transform with respect to the two external momenta, $p_1^2$, $p_2^2=(p-q)^2$. Our result $g_{K^\ast K\pi}=(8.7\pm 0.5)$ and $g_{\rho\pi\pi}=(11.5\pm 0.8)$ is in good agreement with the experimental value.