The interplay of single-particle and collective motions in the low-lying states of 21?Ne with quadrupole-octupole correlations

The beyond mean-field approach for low-lying hypernuclear states is extended by mixing the configurations associated with both single-particle and quadrupole-octupole collective excitations within the generator coordinate method based on a covariant density functional theory. The method is demonstrated in the application to the low-lying states of Ne-21(?), where the configurations with the ? hyperon occupying the first (?(s)) and second (?(p)) lowest-energy states are considered. The results indicate that the positive-parity states are dominated by the a + C-12 + a + ?(s) structure. In contrast, the low-lying negative-parity states are dominated by a strong admixture of a +O-16 + ?(s) structure and a + C-12 + a + ?(p) structure due to the inclusion of octupole correlations. As a result, the low-lying negative-parity states become much lower than what is expected from the previous studies without the mixing, and the electric multipole transition strengths are significantly quenched.