Beyond-mean-field approach to low-lying spectra of $\Lambda$ hypernuclei

TL;DR

This paper develops a beyond-mean-field microscopic particle-rotor model to accurately describe low-lying spectra of hypernuclei, specifically $^{13}_{~ extLambda}$C, accounting for quantum fluctuations and impurity effects of the $ extLambda$ hyperon.

Contribution

It introduces a novel beyond-mean-field approach incorporating particle number and angular momentum projections for hypernuclear spectra analysis.

Findings

The model successfully describes the impurity effects of the $ extLambda$ hyperon.

The main impurity effect in $sd$-shell hypernuclei is a change in deformation, not size.

Quantum fluctuations significantly influence the low-lying spectra.

Abstract

Taking the hypernucleus $^{13}_{~\Lambda}$C as an example, we illustrate the miscroscopic particle-rotor model for low-lying spectra of hypernuclei. This approach is based on the beyond-mean-field method, with the particle number and angular momentum projections. The quantum fluctuation of the mean-field is also taken into account for the core nucleus using the generator coordinate method. We show that the impurity effect of $\Lambda$ hyperon, such as a change in $B(E2)$, is well described with this model. Our calculation indicates that the most important impurity effect in $sd$-shell hypernuclei is a change in a deformation parameter rather than in a nuclear size.