Light quark masses 99

I give a short historical and a critical review of th determinations of light quark masses from QCD at drawn of the next millennium. QCD spectral sum rules combined with ChPT give, to order alpha(3)(3), the world average for the running masses: (m) over bar(s)(2 GeV)= (118.0 +/- 12.2) MeV, (m) over bar(d)(2 GeV) - (6.3 +/- 0.8) MeV, (m) over bar(u)(2 GeV) - (3.5 +/- 0.4) MeV and the corresponding values of the invariant masses given in Eq. 24. Lower and upper bounds derived from the positivity of spectral moments are presented in Tables a and 3. For a comparison, wc critically review the recent lattice results (section 8 and Table 5) and attempt to deduce the present GCD grand average determination (Table 6): (m) over bar(s)(2 GeV)= (110.9+/-8.8) MeV. to be used with a great care. Then, we deduce the value: B-6(1/2) -0.45(resp. 0.32)B-8(3/2) similar or equal to 1.6+/-0.4 (resp. 1.1+/-0.3) and the lower bound 1.1+/-0.2 (resp 0.7+/-0.1), for the combination of the penguin operators, governing the CP-violating parameters epsilon'/epsilon without (resp. with) the inclusion of the final state interaction effects. The result signals a possible deviation from the leading 1/N prediction by about 1 similar to 3 sigma, which should be tested using accurate non-perturbative calculations.