Effective Lagrangians for Light Quarks

Abstract

The class of phenomenological Lagrangians used for light constituent quarks is discussed. The Nambu-Jona-Lasinio model is then argued to be a good phenomenological choice and the quality of its prediction in the purely hadronic sector including several relations between parameters illustrated. Then we use these models to calculate nonleptonic matrix elements. The $π^+-π^0$ mass difference and the $B_K$ parameter, relevant in $K^0-\overline{K}^0$ mixing, are treated in more detail.