New Charm and Bottom Quark Mass Determinations from QCD Sum Rules

In this talk we discuss results of a new extraction of the (MS) over bar charm quark mass using relativistic QCD sum rules at O(alpha(3)(s)) based on moments of the vector and the pseudoscalar current correlators, and using the available experimental measurements from e(+) e(-) collisions and lattice results, respectively. The analysis of the perturbative uncertainties is based on different implementations of the perturbative series and on independent variations of the renormalization scales for the mass and the strong coupling, following a work we carried out earlier. Accounting for the perturbative series that result from this double scale variation is crucial, since some of the series can exhibit extraordinarily small scale dependence, if the two scales are set equal. The new aspect of the work reported here addresses the problem that double scale variation might also lead to an overestimate of the perturbative uncertainties. We supplement the analysis by a convergence test that allows to quantify the overall convergence of QCD perturbation theory for each moment, and to discard series that are artificially spoiled by specific choices of the renormalization scales. We also apply the new method to an extraction of the (MS) over bar bottom quark mass using experimental moments that account for a modeling uncertainty associated to the continuum region where no experimental data is available. We obtain (m) over bar (c)((m) over bar (c)) = 1.288 +/- 0.020 GeV and (m) over bar (b)((m) over bar (b)) = 4.176 +/- 0.023 GeV.