Precision calculations of the $D_{(s)}D_{(s)}V$ and $B_{(s)}B_{(s)}V$ couplings from light-cone sum rules

We present an improved calculation of the $HHV$ ($H=D_{(s)},\, B_{(s)}$, $V= \rho$, $K^\ast$, $\omega$, and $\phi$) coupling constants $g_{HHV}$ beyond leading order in $\alpha_s$ from QCD light-cone sum rules (LCSRs) by means of the light-cone distribution amplitudes (LCDAs) of light vector mesons. Near the light-cone, the next-to-leading order QCD corrections for the vacuum-to-vector-meson correlation function are included at leading power in $\delta_V = m_V/m_Q$ ($Q=b,c$) within the framework of hard-collinear factorization. The higher-twist corrections from two-particle and three-particle vector meson LCDAs are systematically incorporated at leading order in $\alpha_s$ by applying the method of background field in LCSRs. Based on these improvements, we perform a systematic computation of the strong coupling constants $g_{H HV}$ and extract the effective coupling $\beta$ of the heavy meson chiral perturbation theory (HM$\chi$PT). Furthermore, we accomplish the analysis for the relation between the coupling $g_{HHV}$ and the residue of the $H\to V$ transition form factor $A_0$ at heavy pseudoscalar pole. Additionally, we provide a detailed investigation of the $SU(3)$ flavour symmetry breaking effects and conduct a comparative analysis with results from previous studies.