Quenching of the magnetic multipole strength distribution and of the anomalous magnetic moment in complex nuclei and mesonic renormalization of the nuclear spin current

The retardation of the magnetic multipole strength distribution (specifically M1 and M2) extracted from inelastic electron scattering to so-called pion-like states and the quenching of magnetic moments, both in heavy nuclei, is attributed to a mesonic renormalization of the nuclear spin current. The mechanism invoked is the same that leads to the renormalization of the axial current in nuclei and that also governs low energy p-wave pion-nucleus scattering (Lorentz-Lorenz effect). (orig.)