Light Quark Masses and the CP violation parameter $\hat{I}{\mu }^{\prime }/\hat{I}\mu$

Abstract

We present estimates of light quarks masses using lattice data. Our main results are based on a global analysis of all the published data for Wilson and Staggered fermions, both in the quenched approximation and with $n_f=2$ dynamical flavors. The Wilson and Staggered results agree after extrapolation to the continuum limit for both the $n_f=0,2$ theories. Our best estimates, in the MSbar scheme at scale $2GeV$, are $mbar=3.2(4)MeV$ and $m_s=90(20)MeV$ in the quenched approximation, and $mbar2.7MeV$ and $m_{s}70MeV$ for the $n_f=2$ theory. These estimates are significantly smaller than phenomenological estimates based on sum rules, but maintain the ratios predicted by chiral perturbation theory. Along with the new estimates of 4-fermion operators, lower quark masses have a significant impact on the extraction of $\hat{I}{\mu }^{\prime }/\hat{I}\mu$ from the Standard Model.

3 Pages LaTex. Axis files of figures included. Talk presented at LATTICE96 (phenomenology)