We evaluate mass differences between a neutron and a proton, and between a charged and a neutral meson by using a gauged linear sigma model retaining the chiral SU (2) L × SU (2) R × U (1)V symmetry. Masses of nucleons and relevant mesons are generated through the spontaneous and the explicit chiral symmetry breaking. Since our Lagrangian includes explicitly SU(2) isospin symmetry breaking term, it enables us to simultaneously consider the mass differences of a neutron and a proton, and a charged meson and a neutral one. Their reciprocal relations of the mass differences are also derived, where radiative corrections due to electromagnetic interactions are deliberately taken into account to exactly obtain the isospin symmetry breaking effect in the particle mass differences.
Isospin-symmetry breaking and shape coexistence in A∼70 analogs
