Structure of beta-decay strength function S_β(E) and quenching of axial-vector weak interaction constant in halo nuclei

Abstract

Resonance structure of the beta decay strength function Sβ (E) for GT β--decay of halo nuclei 6He and 11Li is analyzed. Compare experimental total strength for β-transitions in gv2/4π units with the Ikeda sum rule (in (gAeff)2/4π units) one can determine the squared ratio of axial-vector and vector weak interaction constants value (g eff/gV)2. We obtained (g eff/gv)1 = 1.272 ± 0.010 for 6He and (gA eff/gv)2 = 1.5±0.2 for 11Li β--decays. Quenching of the weak axial-vector constant gAeff in halo nuclei is discussed. Analysis of the evolution of EGTR - EIAS toward neutron-rich nuclei was done. It is shown that the value Z/N ≈ 0.6 corresponds to the SU(4) Wigner's spin-isospin symmetry region.