Quadrupole deformation(β,γ)of lightΛhypernuclei in a constrained relativistic mean field model: Shape evolution and shape polarization effect of the

Bin Lü

¹

,

En-Guang Zhao

²

,

Shan‐Gui Zhou

³

Abstract

Quadrupole deformation (β, γ) of light Λ hypernuclei in constrained relativistic mean field model: shape evolution and shape polarization effect of Λ hyperon The shapes of light normal nuclei and Λ hypernuclei are investigated in the (β, γ) deformation plane by using a newly developed constrained relativistic mean field (RMF) model. As examples, the results of some C, Mg, and Si nuclei are presented and discussed in details. We found that for normal nuclei the present RMF calculations and previous Skyrme-Hartree-Fock models predict similar trends of the shape evolution with the neutron number increasing. But some quantitative aspects from these two approaches, such as the depth of the minimum and the softness in the γ direction, differ a lot for several nuclei. For Λ hypernuclei, in most cases, the addition of a Λ hyperon alters slightly the location of the ground state minimum towards the direction of smaller β and softer γ in the potential energy surface E ∼ (β, γ). There are three exceptions, namely, 13 Λ C, 23 Λ C, and 31 Λ Si in which the polarization effect of the additional Λ is so strong that the shapes of these three hypernuclei are drastically different from their corresponding core nuclei.

SuperdeformedΛhypernuclei with antisymmetrized molecular dynamics

“…By adding a hyperon to them, it is expected that the low-lying excitation spectra will be modified in Sc hypernuclei, because the B will be different depending on the deformation. Especially, in the case of the hyperon in the s wave, it is predicted that the -separation energy B becomes larger for the spherical state than the deformed state [6,10,[15][16][17]. Therefore, the addition of a particle will affect the low-lying spectra of Sc isotopes, and hence we expect that Sc isotopes are suited to verify the dependence of B on nuclear deformation, which is one of the purposes of this study.…”

Modification of triaxial deformation and change of spectrum inΛ25Mg caused by theΛhyperon

“…Recently, various structure changes have been predicted in sd-shell hypernuclei, because normal sd-shell nuclei have a variety of structures in the ground and low-lying states. For example, it was predicted that the hyperon in s orbit reduces the nuclear deformation [17][18][19][20]23]. On the contrary, the hyperon in p orbit enhances it [20].…”

“…In triaxial deformed nuclei, the response to the addition of the particle will be different from those of axial symmetric nuclei [23,33,34]. 24 Mg is one of the candidates of triaxial deformed nuclei, because of the presence of the K π = 2 + sideband built on the 2 + 2 state at 4.3 MeV [35][36][37][38][39][40].…”

Recent progress in theoretical nuclear physics related to large-scale scientific facilities

“…Compared to the large effect of an additional Λ particle on nuclear deformation in the light soft nuclei within relativistic mean field method [77], this effect is much smaller in the nonrelativistic mean-field approximation. These results have inspired further studies of the shape driven effects of Λ hyperon in atomic nuclei [78][79][80].…”