Two-loop anomalous dimension of the chromo-magnetic moment of a heavy quark

We find that the anomalous dimension (in the MS scheme) of the chromo-magnetic operator gshυσμνGμνhυ in the heavy-quark effective theory is γmag=CAαS2π1+1718CA−1318TFnfαsπ+0(α2s) generalizing the one-loop expression known previously. To derive the two-loop result, we use the reparametrization invariance and the virial theorem. After performing infrared subtractions, all two-loop integrals are of propagator type and are evaluated by a recurrence relation for tensor integrals.