The hyperon puzzle, the observation that the two-solar-mass neutron stars 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. An experimental study of the reaction (e,e′K) on 40Ca 48Ca nuclei to study the isospin dependence of hyperon dynamics has been proposed, by the Jefferson lab hypernuclear collaboration, and approved by the Jefferson Lab (JLab) PAC. This paper describes a proposal to make a complementary study by extending it to 208Pb, whose properties largely reflects those of the uniform nuclear matter present in the interior of the neutron stars making it the ideal one for this task.

The hyperon puzzle, the observation that the two -solar-mass neutron stars 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. An experimental study of the reaction (e,e'K) on Ca-40 Ca-48 nuclei to study the isospin dependence of hyperon dynamics has been proposed, by the Jefferson lab hypernuclear collaboration, and approved by the Jefferson Lab (JLab) PAC. This paper describes a proposal to make a complementary study by extending it to Pb-208, whose properties largely reflects those of the uniform nuclear matter present in the interior of the neutron stars making it the ideal one for this task.

The cross sections for electroproduction of p-shell hypernuclei are calculated in the distorted-wave impulse approximation. Previous calculations performed in the last two decades were updated utilizing new elementary-production amplitudes and new nuclear and hypernuclear structure based on shell-model calculations. Predictions for the formation cross sections and excitation-energy spectra of the Li-9(Lambda), B-12(Lambda), and N-16(Lambda) hypernuclei are compared with the data from JLab experiments and uncertainties of the theoretical results are discussed. We focus on the uncertainties from the elementary amplitude, kaon distortion, and kinematics. Results for the elementary electroproduction of K+ in the hypernuclear-production kinematics are also briefly discussed

This Article is brought to you for free and open access by the Physics at ODU Digital Commons. It has been accepted for inclusion in Physics Faculty Publications by an authorized administrator of ODU Digital Commons. For more information, please contact digitalcommons@odu.edu. Repository Citation Urciuoli, G. M.; Hayes, D.; Hyde, C. E.; Ibrahim, H. F.; Ulmer, P.E.; and Jefferson Lab Hall A Collaboration, "Spectroscopy of Li-9 (Lambda) by Electroproduction" (2015). Physics Faculty Publications. 152. https://digitalcommons.odu.edu/physics_fac_pubs/152

An overview of strangeness nuclear physics is given, focussing on spin dependent effects in Λ hypernuclei, on the ΛN → NN weak interaction in Λ hypernuclei, on the density dependence of the Σ nuclear potential and on double strangeness physics. A special emphasis is placed on the recent proposal to study experimentally Ξ− atoms.

In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei can provide information on the details of the effective hyperon-nucleon interaction. Electroproduction of the hypernucleus Lambda-9Li has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a 9Be target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magnets and a Ring Imaging CHerenkov detector (RICH) were added to the Hall A standard equipment. The cross section to low-lying states of Lambda-9Li is concentrated within 3 MeV of the ground state and can be fitted with four peaks. The positions of the doublets agree with theory while a disagreement could exist with respect to the relative strengths of the peaks in the doublets. A Lambda separation energy of 8.36 +- 0.08 (stat.) +- 0.08 (syst.) MeV was measured, in agreement with an earlier experiment.

L. Tang, 2, ∗ C. Chen, T. Gogami, D. Kawama, Y. Han, L. Yuan, A. Matsumura, Y. Okayasu, T. Seva, V. M. Rodriguez, 6 P. Baturin, A. Acha, P. Achenbach, A. Ahmidouch, I. Albayrak, D. Androic, A. Asaturyan, R. Asaturyan, † O. Ates, R. Badui, O. K. Baker, F. Benmokhtar, W. Boeglin, J. Bono, P. Bosted, E. Brash, P. Carter, R. Carlini, A. Chiba, M. E. Christy, L. Cole, M. M. Dalton, 2 S. Danagoulian, A. Daniel, R. De Leo, V. Dharmawardane, D. Doi, K. Egiyan, M. Elaasar, R. Ent, H. Fenker, Y. Fujii, M. Furic, M. Gabrielyan, L. Gan, F. Garibaldi, D. Gaskell, A. Gasparian, E. F. Gibson, P. Gueye, O. Hashimoto, † D. Honda, T. Horn, 11 B. Hu, Ed V. Hungerford, C. Jayalath, M. Jones, K. Johnston, N. Kalantarians, H. Kanda, M. Kaneta, F. Kato, S. Kato, M. Kawai, C. Keppel, H. Khanal, M. Kohl, L. Kramer, K. J. Lan, Y. Li, A. Liyanage, W. Luo, D. Mack, K. Maeda, S. Malace, A. Margaryan, G. Marikyan, P. Markowitz, T. Maruta, N. Maruyama, V. Maxwell, D. J. Millener, T. Miyoshi, A. Mkrtchyan, H. Mkrtchyan, T. Motoba, 24 S. Nagao, S. N. Nakamura, A. Narayan, C. Neville, G. Niculescu, M. I. Niculescu, A. Nunez, Nuruzzaman, H. Nomura, K. Nonaka, A. Ohtani, M. Oyamada, N. Perez, T. Petkovic, J. Pochodzalla, X. Qiu, S. Randeniya, B. Raue, J. Reinhold, R. Rivera, J. Roche, C. Samanta, Y. Sato, B. Sawatzky, E. K. Segbefia, D. Schott, A. Shichijo, N. Simicevic, G. Smith, Y. Song, M. Sumihama, V. Tadevosyan, T. Takahashi, N. Taniya, K. Tsukada, V. Tvaskis, M. Veilleux, W. Vulcan, S. Wells, F. R. Wesselmann, S. A. Wood, T. Yamamoto, C. Yan, Z. Ye, K. Yokota, S. Zhamkochyan, and L. Zhu

Since the pioneering experiment, E89-009 studying hypernuclear spectroscopy using the $(e,e^{\prime}K^+)$ reaction was completed, two additional experiments, E01-011 and E05-115, were performed at Jefferson Lab. These later experiments used a modified experimental design, the Tilt Method, to dramatically suppress the large electromagnetic background, and allowed for a substantial increase in luminosity. Additionally, a new kaon spectrometer, HKS (E01-011), a new electron spectrometer, HES, and a new splitting magnet were added to produce precision, high-resolution hypernuclear spectroscopy. These two experiments, E01-011 and E05-115, resulted in two new data sets, producing sub-MeV energy resolution in the spectra of ${}^{7}_{\Lambda}\text{He}$, ${}^{12}_{\Lambda}\text{B}$ and ${}^{28}_{\Lambda}\text{Al}$ and ${}^{7}_{\Lambda}\text{He}$, ${}^{10}_{\Lambda}\text{Be}$, ${}^{12}_{\Lambda}\text{B}$ and ${}^{52}_{\Lambda}\text{V}$. All three experiments obtained a ${}^{12}_{\Lambda}\text{B}$, spectrum, which is the most characteristic $p$-shell hypernucleus and is commonly used for calibration. Independent analyses of these different experiments demonstrate excellent consistency and provide the clearest level structure to date of this hypernucleus as produced by the $(e,e^{\prime}K^+)$ reaction. This paper presents details of these experiments, and the extraction and analysis of the observed ${}^{12}_{\Lambda}\text{B}$ spectrum.

Since the pioneering experiment E89-009 studying hypernuclear spectroscopy using the (e,e' K+) reaction was completed, two additional experiments, E01-011 and E05-115, were performed at Jefferson Lab. These later experiments used a modified experimental design, the "tilt method," to dramatically suppress the large electromagnetic background, and allowed for a substantial increase in luminosity. Additionally, a new kaon spectrometer, HKS (E01-011), a new electron spectrometer, HES, and a new splitting magnet (E05-115) were added to produce new data sets of precision, high-resolution hypernuclear spectroscopy. All three experiments obtained a spectrum for B-12(Lambda), which is the most characteristic p-shell hypernucleus and is commonly used for calibration. Independent analyses of these different experiments demonstrate excellent consistency and provide the clearest level structure to date of this hypernucleus as produced by the (e,e' K+) reaction. This paper presents details of these experiments, and the extraction and analysis of the observed B-12(Lambda) spectrum.

The interpretation of hypernuclear γ-ray data for p-shell hypernuclei in terms of shell-model calculations that include the coupling of Λ- and Σ-hypernuclear states is briefly reviewed with emphasis on the successes and outstanding problems. The extension of the shell-model calculations to sd-shell hypernuclei, motivated by an experiment with a 19F target to be performed at J-PARC with the new Hyperball-J, is outlined including a discussion of both positive-parity and negative-parity states in FΛ19.

The characteristics of the Jefferson Lab electron beam, together with those of the experimental equipment, offer a unique opportunity to study hypernuclear spectroscopy via electromagnetic induced (e,e′K+) reactions. Experiment 94-107 started a systematic study on 1p-shell targets, C12, Be9 and O16. For C12 for the first time measurable strength in the core-excited part of the spectrum between the ground state and the p state was shown in the BΛ12 spectrum. For O16 a high-quality NΛ16 spectrum was produced for the first time with sub-MeV energy resolution. A very precise Λ binding energy value for NΛ16, calibrated against the elementary (e,e′K+) reaction on hydrogen, has also been obtained. Preliminary data on the LiΛ9 spectrum shows some disagreement in strength for the second and third doublet with respect to the theory.

Highlights of ΛΛ emulsion events are briefly reviewed. Given three accepted events, shell-model predictions based on p-shell Λ hypernuclear spectroscopic studies are shown to reproduce \(B_{\Lambda\Lambda}({_{\Lambda\Lambda}^{~10}{\rm Be}})\) and \(B_{\Lambda\Lambda}({_{\Lambda\Lambda}^{~13}{\rm B}})\) in terms of \(B_{\Lambda\Lambda}({_{\Lambda\Lambda}^{~~6}{\rm He}})\). Predictions for other species offer judgement on several alternative assignments of the \(_{\Lambda\Lambda}^{~13}{\rm B}\) KEK-E176 event, and on the assignments \(_{\Lambda\Lambda}^{~11}{\rm Be}\) and \(_{\Lambda\Lambda}^{~12}{\rm Be}\) suggested recently for the KEK-E373 HIDA event. The predictions of the shell model, spanning a wide range of A values, are compared with those of cluster models, where the latter are available.

It is shown how the recent shell-model determination of ΛN spin-dependent interaction terms in Λ hypernuclei allows for a reliable deduction of ΛΛ separation energies in ΛΛ hypernuclei across the nuclear p shell. Comparison is made with the available data, highlighting BeΛΛ11 and BeΛΛ12 which have been suggested as possible candidates for the KEK-E373 HIDA event.

Shell-model calculations that include both Λ and Σ configurations with p-shell cores are used to interpret γ-ray transitions in 7ΛLi, 9ΛBe, 10ΛB 11ΛB, 12ΛC, 15ΛN, and 16ΛO observed with the Hyperball array of Ge detectors. It is shown that the data puts strong constraints on the spin dependence of the ΛN effective interaction and that the Λ-Σ coupling plays an important role.

Hiyama et al. [PRL 104 (2010) 212502] have recently reported on a pioneering five-body alpha-alpha-n-Lambda-Lambda cluster-model calculation of Lambda-Lambda-11Be in order to confront a possible interpretation of the KEK-E373 HIDA event. Unfortunately, a six-body alpha-alpha-n-n-Lambda-Lambda calculation of Lambda-Lambda-12Be to confront another possible interpretation is beyond reach at present. Using experimental B-Lambda values with small corrections based on recently determined Lambda-N spin-dependent interaction parameters, we obtain binding-energy shell-model estimates for both Lambda-Lambda hypernuclei, concluding that neither Lambda-Lambda-11Be nor Lambda-Lambda-12Be provide satisfactory interpretation of the HIDA event. The shell model approach is tested by reproducing the measured double-Lambda binding energy of the double-Lambda hypernucleus Lambda-Lambda-13B.

An experimental study of the (16)O(e,e'K(+))(Lambda)(16)N reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e'K(+))Lambda, Sigma(0) exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76+/-0.16 MeV was obtained for (Lambda)(16)N with better precision than previous measurements on the mirror hypernucleus (Lambda)(16)O. Precise energies have been determined for peaks arising from a Lambda in s and p orbits coupled to the p(1/2) and p(3/2) hole states of the (15)N core nucleus.

Shell-model calculations that include both Λ and Σ configurations with p-shell cores are used to interpret γ-ray transitions in LiΛ7, BeΛ9, BΛ10, BΛ11, CΛ12, NΛ15, and OΛ16 observed with the Hyperball array of Ge detectors. It is shown that the data puts strong constraints on the spin dependence of the ΛN effective interaction.