Modification of triaxial deformation and change of spectrum in ${}_{\Lambda }^{25}$Mg caused by $\Lambda$ hyperon

Abstract

The positive-parity states of ${}_{\Lambda }^{25}$Mg with a $\Lambda$ hyperon in $s$ orbit were studied with the antisymmetrized molecular dynamics for hypernuclei. We discuss two bands of ${}_{\Lambda }^{25}$Mg corresponding to the $K^{\pi }=0^{+}$ and $2^{+}$ bands of ${}^{24}$Mg. It is found that the energy of the $K^{\pi }=2^{+}\otimes {\Lambda }_s$ band is shifted up by about 200 keV compared to ${}^{24}$Mg. This is because the $\Lambda$ hyperon in $s$ orbit reduces the quadrupole deformation of the $K^{\pi }=0^{+}\otimes {\Lambda }_s$ band, while it does not change the deformation of the $K^{\pi }=2^{+}\otimes {\Lambda }_s$ band significantly.

Comments: 19 pages, 3 figures