Heavy meson hyperfine splitting: a complete $1/m_Q$ calculation

Abstract

We compute the chiral corrections to the hyperfine splittings ${\Delta }_D=(m_{D_s^{\ast }}-m_{D_s})-(m_{D^{\ast +}}-m_{D^{+}})$ and ${\Delta }_B=(m_{B_s^{\ast }}-m_{B_s})-(m_{B^{\ast 0}}-m_{B^0})$ arising from one-loop chiral corrections, working in a framework of an effective chiral lagrangian incorporating chiral, heavy flavour and spin symmetric terms and first order breaking terms. Among these terms, those responsible for the spin-breaking difference between the couplings $g_{P^{\ast }{P}^{\ast }\pi }$ and $g_{P^{\ast }P\pi }$ are evaluated in the QCD sum rules approach. Their contribution to ${\Delta }_D$ and to ${\Delta }_B$ appears to cancel previously estimated large chiral effects, giving an estimate in agreement with the experimental data.

Comments: 5 pages, latex, no figures. To appear in the Proceedings of the XXXth Rencontres de Moriond, Les Arcs, France, March 1995