January, 2005 Kowalewski --- Perugia lectures 54 HQET Lagrangian The first term is all that remains for m Q →∞; it is clearly invariant under HQ spin-flavour symmetry The terms proportional to 1/m Q are the kinetic energy operator O K for the residual motion of the heavy quark, and the interaction of the heavy quark spin with the color- magnetic field, (operator O G ) The associated matrix elements are non-perturbative; however, they are related to measurable quantities
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