The Renormalization of the Axial-Vector Strength in Nuclei: Experiments on Superallowed Beta-Decay

Abstract

It is known that the empirical coupling constant g<Stack><Subscript>A</Subscript><Superscript>′</Superscript></Stack> characterizing the axial-vector (or, Gamow-Teller) strength in nuclear beta-decay is reduced relative to the free-nucleon value g_A determined from the neutron decay. This reduction, which was first estimated by WILKINSON [1], arises largely from pionic contributions and hence is one of the examples of sub-nucleonic effects in nuclear physics. Very approximately one may say that one part of the effect comes from virtual hole-delta pairs and another part from second-order core polarization brought about by the tensor force, which itself is predominantly due to one-pion exchange. Papers dealing with these problems, and references to earlier work, can be found in publication [2].