ELECTROMAGNETIC SPLITTINGS AND LIGHT-QUARK MASSES IN LATTICE QCD

A method for computing electromagnetic properties of hadrons in lattic e QCD is described and preliminary numerical results are presented. Th e electromagnetic field is introduced dynamically, using a noncompact formulation. Employing enhanced electric charges, the dependence of th e pseudoscalar meson mass on the (anti)quark charges and masses can be accurately calculated. At beta = 5.7 with Wilson action, the pi(+)-pi (0) splitting is found to be 4.9(3) MeV. Using the measured K-0-K+ spl itting, we also find m(u)/m(d) = 0.512(6). Systematic errors are discu ssed.