HQET chromomagnetic interaction at two loops

Abstract

We present the coefficient of the chromomagnetic interaction operator, the only unknown coefficient in the Heavy Quark Effective Theory (HQET) lagrangian up to the $1/m$ level, with the two-loop accuracy by matching scattering amplitudes of an on-shell heavy quark in an external field in full QCD and HQET, and obtain the two-loop anomalous dimension of this operator in HQET.

Comments: 10 pages, LaTeX2e, 2 eps figures included. Revised discussion of (n_f-1)-flavour HQET included