Electromagnetic Splittings and Light Quark Masses in Lattice QCD

Abstract

A method for computing electromagnetic properties of hadrons in lattice QCD is described and preliminary numerical results are presented. The electromagnetic field is introduced dynamically, using a noncompact formulation. Employing enhanced electric charges, the dependence of the 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 $K^0-K^{+}$ splitting, we also find $m_u/m_d=.512(6)$. Systematic errors are discussed.