Improved effective action for light quarks beyond the chiral limit

Abstract.

We propose an improvement of the Diakonov–Petrov effective action on the basis of the Lee–Bardeen results for the quark determinant in the instanton field. This improved effective action provides a proper account of the current quark masses, which is particularly important for strange quarks. This action is successfully tested by calculations of the quark condensate, the masses of the pseudoscalar meson octet and axial-anomaly low-energy theorems.