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The (e, e’K+) reaction experiments with several nuclear targets performed recently at the Jefferson laboratory have provided high-resolution spectroscopic data. Among others, the 10B(e, e’K+) 10ΛBe reaction data are particularly interesting due to new appearance of extra sub-peaks which seem difficult to be explained within the conventional model with the p-shell nuclear naturalparity configurations. To describe this novel hypernuclear structure, we have extended the model space by introducing the new configurations which include unnatural-parity nuclear core-excited states. This configuration mixing successfully explains the sub-peaks in the 10B(e, e’K+) reaction data. For adjacent hypernuclei with A = 9–11, we show the DWIA spectra of (K−, π−), (π+, K+) and (γ, K+) reactions that are calculated within the extended model in a consistent way. We discuss the theoretical spectra of 9,10ΛBe and 11ΛB production reactions.

The hyperon puzzle, the observation that the two-solar-mass neutron star existence is hardly explained by all models predicting the appearance of hyperons in the neutron star core, is currently one of the unsolved key issues in the physics of compact stars. To solve the hyperon puzzle an experimental program has been proposed by the Jefferson lab hypernuclear collaboration and approved by the Jefferson Lab (JLab) PAC. This program consists in the study of the reaction (e, e’K) on 40Ca and 48Ca nuclei, aimed at investigating the isospin dependence of hyperon dynamics, and in the study of the reaction (e, e’K) on 208Pb nucleus, which is the subject of this paper and which will take advantage of the fact that 208Pb properties largely reflects those of the uniform nuclear matter present in the interior of the neutron stars making it the ideal tool to investigate neutron star features. The proposal of the study of the reaction (e, e’K) on 208Pb was approved by the Jlab PAC in 2020.

We intend to study the role of the three-body weak Λ NN → NNN interaction in two-nucleon induced hypernuclear non-mesonic weak decay. The three-body weak interactions are constructed on the basis of the meson-pair exchange (MPE) model and then we derive the effective two-body Λ N → NN weak potentials from the three-body interactions based on the Loiseau–Nogami–Ross approximation. The strong coupling constants of MPE are taken from the Nijmegen ESC and GESC models and the weak ones of MPE are evaluated in the weak Λ– n mixing model by Dalitz and Von Hippel [Phys. Lett. 10 , 153 (1964)]. The effective two-body Λ N → NN weak potentials are applied to evaluate hypernuclear non-mesonic decay rates, which should give a certain additional contribution to the two-nucleon induced decay rate Γ2 N . Calculations of |$\Gamma ^{({\text{eff.2B}})}_{nm}$| are done for |$^5_\Lambda {\rm He}$|⁠ , |$^{11}_\Lambda {\rm B}$|⁠ , and |$^{12}_\Lambda {\rm C}$| and the results are compared with experimental data |$\Gamma ^\mathrm{exp}_{2N}$|⁠. We have demonstrated the possibility of accounting for the two-nucleon induced non-mesonic decays of light and p -shell hypernuclei by introducing the effective two-body potentials deduced from the three-body weak interactions, though the calculated |$\Gamma ^{(\text{eff.2B})}_{nm}$| still includes uncertainties. Discussions and limitations of our "effective two-body Λ N → NN model" are given. [ABSTRACT FROM AUTHOR]

Energy spectra of |$0s$| -orbit |$\Lambda$| states in |$p$| -shell |$\Lambda$| hypernuclei (⁠|$^{A}_\Lambda Z$|⁠) and those in |$^{19}_{\Lambda}\textrm{F}$| are studied with the microscopic cluster model and antisymmetrized molecular dynamics using the |$G$| -matrix effective |$\Lambda N$| (⁠|$\Lambda NG$|⁠) interactions. Spin-dependent terms of the ESC08a version of the |$\Lambda NG$| interactions are tested and phenomenologically tuned to reproduce observed energy spectra in |$p$| -shell |$^{A}_\Lambda Z$|⁠. Spin-dependent contributions of the |$\Lambda N$| interactions to spin-doublet splitting and excitation energies are discussed. Energy spectra for unobserved excited states in |$p$| -shell |$^{A}_\Lambda Z$| and |$^{19}_{\Lambda}\textrm{F}$| are predicted with the modified |$\Lambda NG$| interactions. [ABSTRACT FROM AUTHOR]

Energy level structures of the typical light sd -shell hypernucleus F Λ 19 , together with 18 F, have been studied in detail with the multi-configuration shell model. Both positive-parity and negative-parity nuclear core excitations are fully taken into account by removing the spurious center-of-mass excitation effects. Corresponding to the J-PARC proposal of the 19 F ( K − , π − γ ) F Λ 19 experiment, the production cross sections have been estimated extensively, including the angular distributions. Starting with the elementary amplitudes for the K − n → Λ π − process, the microscopic DWIA calculations at high energy kaon momenta up to 1.8 GeV / c have been carried out for the first time. The calculated wave functions are also used to estimate the electromagnetic transition probabilities for both 18 F and F Λ 19 . The detailed γ -decay schemes are presented and discussed. [ABSTRACT FROM AUTHOR]