First test of the E(5/4) Bose-Fermi symmetry: The structure of Ba-135

Abstract

The first case of a Bose-Fermi critical point symmetry, E(5/4), representing the coupling of a j=3/2 fermion to an E(5) core, was recently proposed. Since Ba-134 has been found to be an empirical manifestation of E(5), we carried out a beta-decay experiment to study levels in Ba-135, where the last neutron can occupy the 2d(3/2) orbit, as the first test of E(5/4). The comparison shows significant areas of agreement as well as significant discrepancies. Comparison of interacting boson-fermion approximation and shell model calculations with the data are also presented.