Recently, scientists from Shandong University, Weihai; Peking University; Beijing University of Aeronautics and Astronautics; Institute of Theoretical Physics, Chinese Academy of Sciences; Tsinghua University; South Africa and Hungary have studied the level structures of Br-78 through the heavy ion fusion evaporation reaction using the accelerator and detector array at iThemba LABS in South Africa. They have found two pairs of chiral doublet bands with opposite parities together with strong electric dipole linking transitions. Calculations based on the covariance density functional theory and particle rotor model indicate that the present observation provides evidence for multiple chiral doublet bands with octupole correlations.
This is the first observation of simultaneous chiral symmetry and reflection symmetry breaking in a single nucleus. It promotes the understanding on spontaneous symmetry breaking in nuclei, and thus has important scientific significance. This work was recently published on Physical Review Letters with the title “Evidence for Octupole Correlations in Multiple Chiral Doublet Bands”, and was chosen as cover. ( link:http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.112501). The first author of this paper is Liu Chen, the PhD student from Institute of space science and physics in Shandong University, Weihai, who is supervised by Prof. Wang Shouyu and Prof. Xia Lidong. Other members from Nuclear and nuclear astrophysics group, Prof. Qi Bin, Dr. Wang Shuo, Mr. Sun Dapeng, and PhD students Liu Lei, Li Zhiquan, Zhang Naibo and Jia Hui, also participated in the present work and made important contribution.
Symmetry and symmetry breaking are fundamental problems in science. Chiral and reflection symmetry breaking widely exist in nature. Chiral symmetry breaking in atomic nuclei has attracted considerable attention and intensive discussion since it was first predicted by Prof. Frauendorf and Prof. Meng. Chirality in nucleus has been confirmed in experiment. The spontaneous reflection symmetry breaking occurs in nuclear with octupole (pear) shaped nucleus, which associates with to charge–parity (CP) violation due to physics beyond the standard model. Members in Nuclear and nuclear astrophysics group led by Prof. Wang Shouyu have devoted themselves to study the spontaneous chiral symmetry breaking in nucleus. They have first opened up the chiral symmetry studies in A~80 mass region internationally and reported the first chiral nucleus in this mass region. Thus A~80 mass region became a new mass region to study chirality completely dominated by the Chinese researchers. The paper published on Physical Review Letters is a natural extension and expansion on the chirality study in the A~80 mass region.
Now this study is supported by China-South Africa intergovernmental S&T Cooperation Project, National Key Basic Research Program of China(973 Program), National Nature Science Foundation of China and Institute of Space Science, Shandong University.
Translated by Liu Chen
Edited by Song Yijun Chen Shangmin