Shape of Lambda hypernuclei in (beta,gamma) deformation plane

TL;DR

This paper investigates the shape and energy surfaces of Lambda hypernuclei in the (beta,gamma) deformation plane using advanced computational methods, revealing how the addition of a Lambda hyperon affects nuclear softness and gamma vibration energies.

Contribution

It provides the first detailed analysis of hypernuclear shapes in the full (beta,gamma) plane using constrained Skyrme Hartree-Fock+BCS calculations, including triaxial deformations.

Findings

Hypernuclei have similar potential energy surfaces to core nuclei.

Adding a Lambda hyperon softens the energy surface along gamma.

Lambda hyperon lowers gamma vibration energy by about 0.15 MeV.

Abstract

We study the shape of $\Lambda$ hypernuclei in the full ($\beta,\gamma$) deformation plane, including both axially symmetric and triaxial quadrupole deformations. To this end, we use the constrained Skyrme Hartree-Fock+BCS method on the three-dimensional Cartesian mesh. The potential energy surface is analyzed for carbon hypernuclei as well as for sd-shell hypernuclei such as $^{27,29}_{\Lambda}$Si and $^{25,27}_{\Lambda}$Mg. We show that the potential energy surface in the ($\beta,\gamma$) plane is similar to each other between the hypernuclei and the corresponding core nuclei, although the addition of $\Lambda$ hyperon makes the energy surface somewhat softer along the $\gamma$ direction. Our calculation implies that the energy of the $\gamma$ vibration for $^{25,27}_{\Lambda}$Mg nuclei is lowered by about 0.15 MeV with respect to that of $^{24,26}$Mg nuclei.