Multiple chiral doublet bands with octupole correlations in reflection-asymmetric triaxial particle rotor model

Abstract

A reflection-asymmetric triaxial particle rotor model (RAT-PRM) with a quasi-proton and a quasi-neutron coupled with a reflection-asymmetric triaxial rotor is developed and applied to investigate the multiple chiral doublet (M$\ddot{I}‡$D) bands candidates with octupole correlations in ${}^{78}$Br. The calculated excited energies, energy staggering parameters, and $B(M1)/B(E2)$ ratios are in a reasonable agreement with the data of the chiral doublet bands with positive- and negative-parity. The influence of the triaxial deformation ${\hat{I}}^3$ on the calculated $B(E1)$ is found to be significant. By changing ${\hat{I}}^3$ from 16${}^{\circ }$ to 21${}^{\circ }$, the $B(E1)$ values will be enhanced and better agreement with the $B(E1)/B(E2)$ data is achieved. The chiral geometry based on the angular momenta for the rotor, the valence proton and valence neutron is discussed in details.

17 pages, 5 figures