Beyond-mean-field study of the hyperon impurity effect in hypernuclei with shape coexistence

Abstract

[Background] The hyperon impurity effect in nuclei has been extensively studied in different mean-field models. Recently, there is a controversy about whether the $\Lambda$ hyperon is more tightly bound in the normal deformed (ND) states than that in the superdeformed (SD) states.[Purpose] This article is aimed to provide a beyond-mean-field study of the low-lying states of hypernuclei with shape coexistence and to shed some light on the controversy.[Method] The models of relativistic mean-field and beyond based on a relativistic point-coupling energy functional are adopted to study the low-lying states of both ${}_{\Lambda }^{37}$Ar and ${}^{36}$Ar. The wavefunctions of low-lying states are constructed as a superposition of a set of relativistic mean-field states with different values of quadrupole deformation parameter. The projections onto both particle number and angular momentum are considered.[Results] The $\Lambda$ binding energies in both ND and SD states of ${}_{\Lambda }^{37}$Ar are studied in the case of the $\Lambda$ hyperon occupying $s,p$, or $d$ state in the spherical limit, respectively. For comparison, four sets of nucleon-hyperon point-coupling interactions are used respectively. Moreover, the spectra of low-lying states in ${}^{36}$Ar and ${}_{{\Lambda }_s}^{37}$Ar are calculated based on the same nuclear energy density functional. The results indicate that the SD states exist in ${}_{\Lambda }^{37}$Ar for all the four effective interactions. Furthermore, the ${\Lambda }_s$ reduces the quadrupole collectivity of ND states to a greater extent than that of SD states. For ${}_{\Lambda }^{37}$Ar, the beyond-mean-field decreases the ${\Lambda }_s$ binding energy of the SD state by 0.17 MeV, but it almost has no effect on that of the ND state. [Conclusions] In ${}_{{\Lambda }_s}^{37}$Ar, the ${\Lambda }_p$ and ${\Lambda }_d$ binding energies of the SD states ...

11 pages, 15 figures, 4 tables, will be published in Phys. Rev. C

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• Disappearance of nuclear deformation in hypernuclei: a perspective from a beyond-mean-field study
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• Intersections of ultracold atomic polarons and nuclear clusters: How is a chart of nuclides modified in dilute neutron matter?
• Beyond mean-field approach for pear-shaped hypernuclei
• The interplay of single-particle and collective motions in the low-lying states of ${}_{\Lambda }^{21}$Ne with quadrupole-octupole correlations
• Quenched Λ spin-orbit splitting by relativistic Fock diagram in single-Λ hypernuclei
• Density-dependent relativistic mean field approach and its application to single-$\Lambda$ hypernuclei in Oxygen isotopes
• Impact of $\Xi$-Hypernuclear Constraints on Relativistic Equation of State and Properties of Hyperon Stars
• Effects of Finite Temperature and Pairing Correlations in Multi-$\Lambda$ Hypernuclei
• Charmed hypernuclei within density-dependent relativistic mean-field theory
• $p$-shell hypernuclear structures using the Gogny-interaction shell model
• Relativistic Mean-Field and Beyond Approaches for Deformed Hypernuclei
• Tetrahedral shape and Lambda impurity effect in ${}^{80}$Zr with a multidimensionally constrained relativistic Hartree-Bogoliubov model