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開放量子系にある軽い不安定核の構造・反応 統一研究とハイパー核への展望

開放量子系にある軽い不安定核の構造・反応 統一研究とハイパー核への展望. M. Ito and N. Itagaki. RIKEN-Nishina-Center, RI Physics Laboratory, RIKEN. Department of Physics, Univ. of Tokyo. IKEDA Diagram. Cluster structures in 4N nuclei. Ikeda’s Threshold rules. Molecular structures will appear

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開放量子系にある軽い不安定核の構造・反応 統一研究とハイパー核への展望

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  1. 開放量子系にある軽い不安定核の構造・反応 統一研究とハイパー核への展望 M. Ito and N. Itagaki RIKEN-Nishina-Center, RI Physics Laboratory, RIKEN Department of Physics, Univ. of Tokyo

  2. IKEDA Diagram Cluster structures in 4N nuclei Ikeda’s Threshold rules Molecular structures will appear close to the respective cluster threshold. αParticle ⇒ Stable B.E. ～ 28 MeV 3H+p ～ 20 MeV Systematic Appearance of a cluster structures

  3. Nuclear clustering in N-rich nuclei 1. a-clustering in stable nuclear systems 20Ne = a + 16O 8Be = 2a、 12C = 3a、 16O = a + 12C、 2. Clustering in N-rich systems : Clusters + XN a a Example : Be isotopes = 2a +XN Molecular Orbital model : N. Itagaki et al., PRC61,62 (2000)

  4. Studies on Exotic Open Quantum Systems in (Ex,T,S,A) Space Slow Exotic beam Open Quantum Systems Today’s report Decays into Continuum Is Threshold Rule valid ?? Structure : 12Be scattering : a+8He Ex. energy Structural Change Low-lying Mol. Orbital : p―、s＋‥ Y N ( S,T,A ) : Three Dimensions

  5. Cluster Physics in N-rich systems Cluster + Valence neutrons Coupling between clusters and neutrons Various configurations will be generated. a a Molecular or Atomic configuration ? In Be isotopes… xHe Clusters Covalent SD Melting or developing of α cluster Atomic orbitals Molecule-Atom Molecular Orbital Low-lying states Coexists in continuum states 10Be : E(5He+5He)－E(a+6He) = 2.75 MeV 12Be : E(6He+6He)－E(a+8He) = 1.16 MeV

  6. 第一原理計算の最近の進展 の例 : GFMC計算 S.C.Pieper et al., PRC70 (04) R.B.Wiringa et al., PRC62 (00) 裸の核力から8Be=a+a構造を記述 励起状態の計算も成功した?? LS結合、置換対称性の異なる 励起状態のみ記述可能 波動関数の空間部分で直交する励起 状態の記述は困難である !! 12C 例えば12C の励起0+は記述は困難 a a a a a a G.S. 02+ (No Core Shell Modelも同様)

  7. j(0p) Framework ( I ) : Single particle motion in two centers F ( s.p.) =j(L) ± j(R) : LCAO jL(0p) ± jR(0p) Y(1,±1) s- ＋ 1/2- (pf) 1/2+ (sd) Y(1,0) p+ ― 3/2+ (sd) Z 1/2- (0p) s+ ― 1/2+ (sd) 3/2- (0p) a a p- ＋ S Config. Mixing Distance : S

  8. Framework ( II ) : Transformation to Atomic orbitals (s+)2 = ( pz(L) － pz(R) )2 = pz(L)・pz(L) + pz(R)・pz(R) ― 2pz(L)・pz(R) 6He + a a + 6He 5He + 5He Generalized Two-center Cluster Model : PLB588 (04) ... S + + Y = PJ C2 C3 C1 S, Ci: Variational PRM 0Pi (i=x,y,z) Coupled channel of Atomic Orbital 10Be=a+a+N+N a 6He 5He 5He Mol. Orb Combne

  9. Intrinsic structures at Local minima Adiabatic Energy surfaces 6He 6He n(0p)6 Jp = 0+ (p-)4 Covalent SD 6He + 6He a + 8He n(0p3/2)4(sd) 2 S～5fm 2 MeV Atomic-Molecular Hybrid configuration (p-)2 (s+)2

  10. Open quantum system : Coupling to open channels in continuum Closed states method : Prof. Kamimura, Prog. Part. Nucl. Phys. 51 (2003) Compound states (Closed) Open channels B.S. solutions with Atomic Orbitals Basis Scattering B.C. Rearrangement channels :a + 8Heg.s.、 6Heg.s. + 6Heg.s.、5Heg.s. + 7Heg.s.

  11. Cross sections of neutron transfers a + 8He ⇒ 6He + 6He a + 8He ⇒ xHe + yHe Elastic | Sf,I |2 Cross sections ( mb ) 6He + 6He 5He + 7He Ec.m. ( MeV ) Ec.m. ( MeV ) Dotted curves : Three open channels only This is prediction for future experiments at GANIL. Solid curves: Open + closed chanels

  12. Excitation from the 02+ state. Excitation modes in 12Be 7He 5He (0pR)(0pL)(s+)2 a+8He ⇒ 6He+6He 06+ 6He 6He 05+ Cluster + S. P. Excitation 04+ Single particle Excitation 03+ Cluster’s relative Motion is excited. 8He (p-)4 Excitation from the 01+ state. 02+ 01+ (p-)2 (s+)2

  13. Rotational bands : Coexistence of MR and covalent SD Green : 5He + 7He Red : Covalent SD Pink : 6He + 6He Blue : a + 8He Black circle: (p-)2(s+)2 White square: (p-)2(p-)2 Exp. by Freer Exp. by Saito Exp. by Shimoura

  14. Lampha (0s)6 Molecular states in Be with multi-L a a K. Ikeda et al., Supp. Prog. Theor. Phys. 81 Stable ?? a a MO will be favored. (0s Mol. Orb.) (5He+5He)－(a+6He) 2.75 MeV 1.01 MeV (now) 4.56 MeV (old) BLL(6LLHe) = 10.8 MeV (old) BLL(6LLHe) = 7.25 MeV (now)

  15. Characteristic properties of Y-N interaction Conversion of hyperons N⊿ Single Λ hypernuclei Coherent L-S coupling Y. Akaishi, PRL84 (00) Σ 250 MeV 80 MeV Λ NN N N N N + N Λ N Σ 4He Λ

  16. 6LHe、 6LLHe、 7LHe、etc… Y. Akaishi, PRL84 (00) In N-rich systems, incoherent mixing effect may appear.

  17. Dimers in (S,T) rich systems Competitions and coexistence of Atomic and Molecular states are very interesting in (E,S,T,A). L Neutron LN-SN coupling 3H a a 3H Incoherent for t-L Coherent for t-L Incoherent for L-N a a 3H 3H Incoherent for L-N More stable than 12Be Incoherent for L-N a a a

  18. まとめ A. Open quantum systemsとしてのハイパー核、不安定核の研究 有限量子多体系の存在形態とダイナミクスを、4次元パラメータ空間(E,S,T,A)内で 探索する研究と位置付けられる｡ B. 軽い領域での特徴 1.クラスター－価粒子間の相互作用は弱いため、これらの自由度の結合様式の違い により多様な構造が発現する。 2. 開放系では、クラスターと価粒子の自由度が励起したエキゾチック構造が多数 共存する ことが予想される。(不安定核10,12Beの結果から) ⇒反応ダイナミクスと構造をリンクした研究が本質的に重要である。 ハイパー核研究 : 反応と構造のタイアップ(但し、主に粒子束縛状態の生成反応) 不安定核研究 : 反応と構造の分業化⇒統一した取り扱いが重要 C. これから Open quantum systemsとしての多中心エキゾチック系の研究は完全にOpen Areaである。従って、0s-shellの2クラスター構造の研究がまず重要であろう。

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