Binding, bonding and charge symmetry breaking in Λ-hypernuclei

Recent experiments have presented more accurate data on the ΛΛ-binding energies of a few ΛΛ-hypernuclei. This is important as the ΛΛ-bond energies (ΔBΛΛ) of double-Λ hypernuclei provide a measure of the in-medium strength of the ΛΛ-interaction. A mass formula, optimized with the newly available ΛΛ binding energy data, is used to estimate the binding energy and bond energy over a wide range of hypernuclei. The ΔBΛΛ values calculated with this mass formula are in good agreement with the experimental data and the predictions of the quark mean-field (QMF) and relativistic mean-field (RMF) models, except at low mass region where large uncertainties exist in the current experimental data. The ΛΛ-bond energies in ΛΛ-hypernuclei are found to diminish with neutron numbers, approaching zero near the neutron-drip line. In this formalism, the calculated binding energy difference in mirror nuclei arises from the Coulomb contributions and can be utilized to extract the Coulomb-corrected charge symmetry breaking effect in mirror Λ-hypernuclei. Our calculations show the regions where more experimental data are needed for light and neutron-rich Λ and ΛΛ-hypernuclei.