Explicit isospin symmetry breaking inSU(2) Skyrme-type models

Abstract

We propose a new mass term which, when added to the standard SU(2) Skyrme model Lagrangian, leads to explicit isospin symmetry breaking in the mesonic sector and also allows -at least when the stabilizing Skyrme term is neglected -for classical (time dependent) "hedgehog" soliton solutions which constitute a basis for the description of physical baryon states with the standard collective coordinate method. At the same time the formalism provides the possibility to correctly reproduce the isospin splitting of the nucleon masses.