Non-Abelian Dipole Radiation and the Heavy Quark Expansion

Abstract

Dipole radiation in QCD is derived to the second order in $\alpha_s$. A power-like evolution of the spin-singlet heavy quark operators is obtained to the same accuracy. In particular, ${\cal O}(\alpha_s^2)$ relation between a short-distance low-scale running heavy quark mass and the $\barMS$ mass is given. We discuss the properties of the effective QCD coupling $\aw(E)$ which governs the dipole radiation. This coupling is advantageous for heavy quark physics.