Recent status in Hypernuclear Physics

1. Recent status in Hypernuclear Physics E. Hiyama (Nara Women’s Univ.)

2. The discussion about the recent progress in the hypernuclear physics by introducing my studies performed so far. My study Λ Λ Λ nucleus nucleus Single Λ hypernucleus Double Λ hypernucleus

3. In 2008 (next year), the construction of J-PARC facility is complete. And the experiment about hypernuclear physics will be run since 2008. So, we expect to have a lot of data of hypernuclei in the future. What are interesting and important to study Hypernuclear physics?

4. Before answering this question, firstly I intoruduce the obtained hypernuclear experimental data so far. Before 1995 • hyperon(Y)-nucleon(N) and hyperon(Y)-hyperon(Y) scattering data

5. Hyperon-nucleon scattering experimental data obtained so far Total number of data:40 NN:4,000 No YY scattering data (Due to the difficulty of the YN and YY scattering experiment)

6. (2) How many single Λ hypernuclei and double Λ hypernuclei were observed so far?

7. (2)いくつハイパー核は見つかっているの？ Λハイパー核について 全部で30個くらい Nuclear chart of a single Λ hypernuclei About 30 events

8. Double Λ hypernuclei 6He ,10Be, 13B ΛΛ ΛΛ ΛΛ There are ambiguities in identifying these double Λ hypernuclei.

9. (3) How many γ transitions were measured? 2+ 5/2+ 1+ γ γ γ 1/2+ 0+ 0+ 7Li 4H 9Be Λ Λ Λ 1- Only excitation energies were measured. γ 0+ B(E2) and B(M1) values NEVER have been observed. 13C Λ

10. Since 1995 We have been obtaining epoch-making experimental data continuously because of development of experimental method, especially, development of high resolution γ-ray spectroscopy method with Ge detector. Some of the recent epoch-making experimental data

11. For the first time, the B(E2) value in 7Li was successfully • observed by KEK-E419. Λ Λ 6Li 7Li Λ As a consequence, we could extract the hypernuclear size for the first time.

12. (2) γ-ray spectroscopic experiments of 9Be and 13C were successfully performed at BNL-E929 and E930. Λ Λ Λ Λ 8Be 12C 9Be 13C Λ Λ As a result, we could determine the strength of ΛN spin-orbit force.

13. (3) At KEK-E373 experiment, a double Λ hypernucleus was observed and was identified uniquely 6He. ΛΛ Λ Λ This is the first observation of double Λ hypernuclei with NO ambiguity. α 6He ΛΛ

14. Furthermore, At J-PARC, we are planning to have many single Λ hypernuclei and double Λ hypernuclei in the future. Why is it important to produce many single Λ hypernuclei and double Λ hypernuclei?

15. Major goal of hypernuclear physics • To understand the hyperon(Y)-nucleon(N) • and hyperon(Y)-hyperon(Y) interaction But since the scattering YN scattering data is limited, then it is necessary to obtain information on YN and YY interactions from the hypernuclear structure study. (2) To study new dynamics of many body systems consisting of nucleons and hyperons For this purpose, we need to have many hypernuclei and double Λ hypernuclei. The J-PARC facility is the key facility to provide the data necessary to attain the goal of hypernuclear physics.

16. The J-PARC facility is the key facility to provide the data necessary to attain the goal of hypernuclear physics. My role To use high precision calculational method of few-body systems to carry out the goal (1) and (2).

17. Applied to Gaussian Expansion Method Developed by Kyushu Univ. group Kamimura (1) 3-cluster structure of light nuclei (2) Coulomb 3-body muonic molecular ions appearing in the muon-catalyzed fusion cycles (1987～) (3) 3-nucleon bound states with realistic NN and 3N forces (1988) (4)Metastable antiprotonic helium atom (He++p+e)(1995～) E. Hiyama, M. Kamimura and Y. Kino, Prog. Part. Nucl. Phys. 51 (2003), 223.

18. This method also successfully applied to four-body problems. • The merit of this method: • To calculate the energy of bound state • very accurately • (2) To calculate the wavefunction very precisely One example

19. Benchmark test of 4He Phys. Rev.C64, 044001(2001) 4He n n p p 4 nucleon bound state NN:AV8

20. Good agreement among 7different method In the binding energy, r.m.s, and two-body correlation function

21. Our method → hypernuclear structure Major goal of hypernuclear physics • To understand the hyperon(Y)-nucleon(N) • and hyperon(Y)-hyperon(Y) interaction Since YN scattering experiment are difficult to perform, the existing data is very limited. So far proposed YN interactions have a large degree of ambiguity. Nijmegen model, Julich model Quark model based potential

22. It is necessary to obtain useful information on YN and YY interaction from hypernuclear structure study.

23. Our calculation of few-body systems play essential role in this connection between the basic models and the experimental data. This theoretical component is our calculational contribution from few-body systems.

24. Discussion on γ-ray spectroscopy experiment and theoretical structure calculations of 9Be and 13C related to the YN spin-orbit interaction Λ Λ Λ Λ 8Be 12C 9Be 13C Λ Λ Strong NN spin-orbit force which leads to magic number nuclei How large is the YN spin-orbit force compared with the NN spin-orbit force?

25. Meson theory Nijmegen model Constituent quark model « Proposed by Fujiwara et al. If we use these types of spin-orbit forces in hypernuclear structure calculation, then how is the spin-orbit energy splitting?

26. O.Morimatsu et al. Nucl. Phys. A420,573 (1984) Why is the spin-orbit force is small based on the constituent quark model ? The strength of Antisymmetric LS(ALS) is opposite sigh with the symmetric LS(SLS). And that of ALS is cancelled that of SLS. ALS : σ ー　σ Λ N xL VALS 2 σ ＋　σ SLS: VSLS Λ N xL 2 Thus, quark model leads to small spin-orbit splitting energy in hypernuclear structure,

27. BNL-E930 Λ 3/2+ γ ΔE Ls splitting 2+ 5/2+ γ 0+ 1/2+ 8Be 9Be Λ 1/2- BNL-E929 ΔE Λ 3/2- γ γ 0+ 1/2+ 13C 12C Λ

28. E. Hiyama et al. Phys. Rev. Lett. 85, 270 (2000) Λ α α α α 8Be = 9Be= Λ α 12C = α α α 13C= Λ Λ α α

29. BNL-E930 3/2+ 5/2+ +2.5 31.4 keV Exp. -3.6 H. Akikawa et al. Phys. Rev. Lett. 88,(2002) 82501. BNL-E929 1/2- 3/2- 152 54 36 keV ± ± S.Ajimura et al. Phys. Rev. Lett. 86,(2001) 4255 ΛN spin orbit force and 9Be and 13C Λ Λ 9Be Λ 35 40 keV 3/2+ 80 200 keV 3/2+ ～ ～ 5/2+ 5/2+ Quark Meson 13C Λ 150 200 keV 1/2- 360 960 keV 1/2- ～ ～ 3/2- Exp. 3/2- Quark Meson

30. When any new types of YN interaction are proposed in the future, it is desirable to pay attention to having a reasonable strength of YN spin-orbit force by testing it in the structure calculation of 9Be and 13C. Λ Λ

31. Where do we go from here? How large are the ΣN and ΛΛ spin-orbit forces? ・ΣN scattering experiments at J-PARC facility ・γ-ray spectroscopy experiments of double Λ hypernuclei Λ Λ nucleus

32. We are extracting novel information about YN interaction because of the cooperation analysis involving the γ-ray spectroscopy experiment and highly accurate calculations. Once the Hamiltonian is determined, we can calculated precisely the structure of many-body systems consisting of neutron, proton and hyperon. Furthermore, we can predict with understanding new phenomena such as we have never imagined before.

33. Major goal of hypernuclear physics • To understand the hyperon(Y)-nucleon(N) • and hyperon(Y)-hyperon(Y) interaction (2) To study new dynamics of many body systems consisting of nucleons and hyperons The J-PARC facility is the key facility to provide the data necessary to attain the goal of hypernuclear physics.

34. (2) To study new dynamics of many body systems consisting of only nucleons One of the major goal in neutron rich nuclear physics (to my knowledge) In unstable nuclear physics When many nucleons are added to the stable nucleus, how is structure? n stable nucleus n

35. In hypernuclear physics nucleus Hyperon(Λ、Ξ・・) How is structure, when hyperons are added to the nucleus? In this view point, we have the same interest both in studying unstable nuclear physics and hypernuclear physics.

36. What is interesting in unstable nuclear physics? one nucleon is added to the nucleus N Pauli principle cluster cluster The valence nucleon is located outside the nucleus. Nucleus consisting of 2 clusters

37. What is interesting in unstable nuclear physics? More nucleons are added to the nucleus・・・ N ・where are additional nucleons are located in the nucleus? ・Do additional nucleons contribute to the dynamical change of structure of 2 clusters? ・Do additional nucleons affect to the critical stability of the nucleus? cluster cluster N N Nucleus consisting of 2 clusters

38. Λ Hypernuclear physics Λ Λ particle can reach deep inside, and attract the surrounding nucleons towards the interior of the nucleus. There is no Pauli Pricliple between N and Λ. Nucleus Hypernucleus Glue-like role of Λ particle As a results, if a Λ particle is added to the nucleus, the resultant hypernucleus will become more stable against the neutron decay. hypernucleus Λ γ nucleus

39. Glue-like role of Λ particle play a crucial role in binding energy mechanism, critical stability. From the view point of the ‘critical stability’, n n N N N N n Λ Λ α α N Λ Λ Λ 4H 4H 6He 7He Λ ΛΛ Λ Λ

40. Λ Hypernuclear physics Λ Λ particle can reach deep inside, and attract the surrounding nucleons towards the interior of the nucleus. There is no Pauli Pricliple between N and Λ. Nucleus Hypernucleus Glue-like role of Λ particle As a results, if a Λ particle is added to the nucleus, the resultant hypernucleus will become more stable against the neutron decay. hypernucleus Λ γ nucleus

41. Example n n Λ Λ α + α 6He Λ ground state is bound. 5He:ground state is unbound n n n n Λ Λ α + α 7He 6He:famous halo nucleus Λ

42. Λ P3/2 0.89 MeV α +n+Λ 0 MeV α +n 5He 5He+n Λ -3.12 MeV 0.17 MeV 1- 6He n Λ α Λ Λ n halo ? L=0 5He α 6He Λ Λ How do the 3 particle locate to each other ? Is there neutron halo in 6He hypernucleus? Λ

43. ^ 密度　　ρn(r) = ∫|Ψ(6He)|2dRdr Λ Λ α r n r.m.s α-Λ 2.8 fm α-n 5.0 fm Larger than 6He Halo nucleus 6He α-n 4.5 fm

44. Λ Example: 7He N 6He : One of the lightest n-rich nuclei N α N N 7He: One of the lightest n-rich hypernuclei Λ Λ α No data

45. E. Hiyama et al. 6He 7He Λ Phys. Rev. C53, 2075 (1996) Prompt particle decay No data 2+ γ α+Λ+n+n 0 MeV 0 MeV α+n+n 5He+n+n 0+ Λ -0.69 7/2+ Halo state 5/2+ -4.43 BΛ=5.44 MeV (cal.) γ 1/2+ -6.12

46. 6He 7He Λ Prompt particle decay No data 2+ γ α+Λ+n+n 0 MeV 0 MeV α+n+n 5He+n+n 0+ Λ -0.69 7/2+ Halo state 5/2+ -4.43 BΛ=5.44 MeV (cal.) γ 1/2+ -6.12 5/2+→1/2+ 3/2+ →1/2+ ・Useful for the study of the excitation mechanism in n-rich hypernuclei ・Helpful to the study of the excitation mechanism of the halo nucleus In n-rich nuclei and n-rich hypernuclei, there will be many examples such as Combination of 6He and 7He. I hope that γ-ray spectroscopy of n-rich hypernuclei will be performed at J-PARC. Λ

47. Schematic illustration of the nuclear chart S=-1 N S=0 N S=0 Most of the n-rich or p-rich nuclei near the drip line have halo- or skin-structure. Outside the drip line, there must be many nucleon-unbound states. What will happen, if we inject a Λ hyperon to those nuclei near the drip line? S=-1 We can expect that the glue-like role of Λ extends the nucleon drip line to more outside.

48. N N N N N Λ Λ Λ 4He 4H Λ ΛΛ Particle-conversion such as ΛN → ΣN is very important in critical stability of few-body hypernuclear systems.

49. In non-strangeness nuclei N⊿ 250 MeV ⊿ N + NN N N N N 3H,3He It is well known that the ground state of 3H and 3He are deeply Bound without ⊿ contribution.

50. Single Λ hypernuclei N⊿ Σ 250 MeV 80 MeV Λ NN N N N N + N Λ N Σ 4He Λ If NNNΣ channel is neglected, then the ground state of 4He is bound or unbound? Λ