Evidence for pseudospin-chiral quartet bands in the presence of octupole correlations

S Guo ,Y.h Zhang ,A Goasduff ,E Dupont ,A Boso ,P W Zhao ,K Ortner ,D Bazzacco ,G.s Li ,F H Garcia ,B Cederwall ,J J Valiente-Dobón ,D Mengoni ,Bo Lyu ,K Whitmore ,S Riccetto ,Jie Meng ,E A Lawrie ,C Andreoiu ,F Recchia ,A Astier ,T Bäck ,S.q Zhang ,A Ataç-Nyberg ,G Jaworski ,J Srebrny ,D R Napoli ,Y H Qiang ,T Marchlewski ,Hongjun Fan ,M Siciliano ,C M Petrache ,F Galtarossa ,I Kuti ,D Testov ,J.g Wang ,Yaozheng Wang ,D Sohler ,X H Zhou ,M.l Liu ,A Tucholski

doi:10.1016/j.physletb.2020.135572

Abstract

Three nearly degenerate pairs of doublet bands are identified in 131Ba. Two of them, with positive-parity, are interpreted as pseudospin-chiral quartet bands. This is the first time that a complete set of chiral doublet bands built on the pseudospin partners π(d5/2,g7/2) is observed. The chiral bands with opposite parity built on 3-quasiparticle configurations are directly connected by many E1 transitions, without involving an intermediary non-chiral configuration. The observed band structures in 131Ba have been investigated by using the reflection-asymmetric particle rotor model. The energies and the electromagnetic transition ratios of the three pairs of doublet bands observed in 131Ba are reproduced and they are interpreted as chiral doublet bands with three-quasiparticle configurations. It is the first time that multiple chiral bands are observed in the presence of enhanced octupole correlations and pseudospin symmetry.

Highlights

Near degeneracy between two quantum states is usually associated with fundamental symmetries and symmetry breakings in complex many-body systems like atomic nuclei
⌫h11/2 are observed in 131 Ba, which represent the first evidence of pseudospin-chiral quartet bands
Pseudospin symmetry is found to play an important role in nuclei with stable triaxial deformation

Summary

Introduction

Near degeneracy between two quantum states is usually associated with fundamental symmetries and symmetry breakings in complex many-body systems like atomic nuclei. Pseudospin symmetry was introduced to describe energy degeneracy between singleparticle states with quantum numbers (n, l, j = l + 1/2) and After proving itself to be critical for many phenomena such as quantized alignment [5], identical bands [6], and pseudospin partner bands [7], the pseudospin was found to be fundamental as a relativistic symmetry of the Dirac Hamiltonian [8]. It has been predicted to remain an important physical concept [11, 12]. This prediction has not been confirmed experimentally

Results

Discussion

Conclusion