MASS DEFINITION IN HEAVY-QUARK EFFECTIVE THEORY AND A NEW DETERMINATION OF V-CB

Positive powers of the mass parameter in a physical quantity calculated with the help of heavy quark effective theory (HQET) originate from a Wilson coefficient in the matching of a QCD and a HQET Green function. We show that this mass parameter enters the calculation as a well-defined running current mass. We further argue that the recently found ill definition of the pole mass, which is the natural expansion parameter of HQET, does not affect a phenomenological analysis which uses a truncated perturbative series. We reanalyze inclusive semileptonic decays of heavy mesons and obtain the c quark mass m(c)(($$$) over bar MS) (m(c)) = (1.35 +/- 0.20) GeV where the error is almost entirely due to scale, uncertainties. We also obtain m(b)(($$$) over bar MS) (m(b)) = (4.6 +/- 0.3) GeV and \V-cb\(T-B/1.49 ps)(1/2) = 0.036 +/- 0.005 where the errors come from the uncertainty in the kinetic energy of the heavy quark inside the meson, in the experimental branching ratios, in QCD input parameters, and scale uncertainties.