ΛNN input to neutron stars from hypernuclear data

This work is a sequel to our two 2023 publications [PLB 837 137669, NPA 1039 122725] where tting 14 1s_Λ and 1pΛ single-particle binding energies in hypernuclei across the periodic table led to a well-de ned Λ-nucleus optical potential. The potential consists of a Pauli modi ed linear-density (ΛN) and a quadratic-density (ΛNN) terms. The present work reports on extending the above analysis to 21 Λ single-particle data points input by including 1d_Λ and 1f_Λ states in medium-weight and heavy hypernuclei. The upgraded results for the ΛN and ΛNN potential depths at nuclear-matter density ρ₀ = 0.17 fm⁻³, D_Λ⁽²⁾ = −37.5 ∓ 0.7 MeV and D_Λ⁽³⁾ = +9.8 ± 1.2 MeV together with the total depth D_Λ = −27.7 ± 0.5 MeV, agree within errors with the earlier results. The Λ hypernuclear overbinding associated with the ΛN-induced potential depth D_Λ⁽²⁾ agrees quantitatively with a recent combined analysis of low-energy Λp scattering data and correlation functions [PLB 850 (2024) 138550]. These results, particularly the size of the repulsive D_Λ⁽³⁾, provide an essential input towards resolving the 'hyperon puzzle' in the core of neutron stars. We also show that a key property of our ΛNN-induced potential term, i.e. a need to suppress the quadratic-density ΛNN term involving an excess neutron and a nucleon in the N = Z core, can be tested in the forthcoming JLab E12-15-008 experiment.