Eur. Phys. J. A (2025) 61: 278
https://doi.org/10.1140/epja/s10050-025-01757-5

Regular Article - Theoretical Physics

$\mathrm{\Lambda }\mathrm{\Lambda }$ interaction in multi-$\mathrm{\Lambda }$ hypernuclei of O and Ca isotopes

¹ Department of Physics, School of Science, Tianjin University, 300354, Tianjin, China
² Department of Physics, Tohoku University, 980-8578, Sendai, Japan
³ RIKEN Nishina Center, 351-0198, Wako, Japan
⁴ Center for Mathematics and Physics, The University of Aizu, 965-8580, Aizu-Wakamatsu, Fukushima, Japan

^a yzhangjcnp@tju.edu.cn

Received: 5 September 2025
Accepted: 21 November 2025
Published online: 10 December 2025

Abstract

Taking the stable and neutron-rich oxygen and calcium isotopes as cores, we investigate the structure of multi-$\mathrm{\Lambda }$ hypernuclei with the Skyrme Hartree–Fock–Bogoliubov model. So far, the observed rare double-$\mathrm{\Lambda }$ hypernuclei events can only provide information for the S-wave $\mathrm{\Lambda }\mathrm{\Lambda }$ interaction, but not for the P-wave. Therefore, in this paper we perform several trials of the strength of P-wave $\mathrm{\Lambda }\mathrm{\Lambda }$ interaction, and discuss its effect on the properties for the multi-$\mathrm{\Lambda }$ hypernuclei. We find that different strengths of P-wave interaction will influence the $\mathrm{\Lambda }$ hyperon drip line in the neutron-rich hypernuclei, but not much in the hypernuclei with a stable core. The diffused $\mathrm{\Lambda }$ hyperon mean-field potential in the neutron-rich core makes the single $\mathrm{\Lambda }$ orbits more bound than in the stable core. Thus, the $\mathrm{\Lambda }$ continuum states are easier to be pulled down to be weakly bound states with attractive P-wave interaction strength as more $\mathrm{\Lambda }$ hyperons are added.