Heavy Meson Hyperfine Splitting: A Complete $1\mathrm{/}{m}_Q$ Calculation

The hyperfine splittings ${\mathrm{\Delta }}_D=(m_{D_s^{\ast }}-m_{D_s})-(m_{D^{\ast +}}-m_{D^{+}})$ and ${\mathrm{\Delta }}_B=(m_{B_s^{\ast }}-m_{B_s})-(m_{B^{\ast 0}}-m_{B^0})$ are analyzed in the framework of an effective lagrangian possessing chiral, heavy flavour and spin symmetries, explicitly broken by a complete set of first order terms. Among these terms, those responsible for the difference between the couplings $\text{gis}$ and $\text{gi}$ are evaluated in the QCD sum rules approach. Their contribution to ${\mathrm{\Delta }}_D$ and to ${\mathrm{\Delta }}_B$ appears to quantitatively balance previously estimated chiral effects nice agreement with the experimental data, solving a suspected puzzle for heavy quark theory.