Light Quark Masses with an O(a)-Improved Action
  We present the recent Fermilab calculations of the masses of the light quarks, using tadpole-improved Sheikholeslami-Wohlert (SW) quarks. Various sources of systematic errors are studied. Our final result for the average light quark mass in the quenched approximation evaluated in the $\bar{MS}$ scheme is $\bar{m}_q(\mu=2 GeV;n_f=0)= (m_u+m_d)/2=3.6 \pm 0.6 MeV$. 
T. Onogi, A.X. El-Khadra, B.J. Gough, G.M. Hockney, A.S. Kronfeld,   P.B. Mackenzie, B.P. Mertens, J.N. Simone