1. Coulomb breakup of the two-neutron halo nucleus 11 Li Takashi Nakamura Tokyo Institute of Technology International Conference on Finite Fermionic Systems Nilsson Model 50 Years June 14-18 2005, Lund, Sweden

2. T.Nakamura, A.M. Vinodkumar, T.Sugimoto, N.Fukuda, M.Miura, Y.Kondo, N.Aoi, N.Imai, T.Kubo, T.Kobayashi, T.Gomi, A.Saito, H.Sakurai, S.Shimoura,D.Bazin, H.Hasegawa, H.Baba, T. Motobayashi, T.Yakushiji, Y. Yanagisawa, K.Yoneda, K. Watanabe, Y.X.Watanabe, M.Ishihara

3. Coulomb Breakup 11 Li High-Z Target (Pb) 9 Li n  = N E1 (E x ) dB(E1) dE x d  CD dE x 9hc 16  3 Cross section = (Photon Number)x  Transition Probability) Invariant Mass ~70MeV/nucleon (  ~0.4 c ) Equivalent Photon Method Introduction 11 Li* n

4. 11 Be – One neutron Halo Case ExEx 10~20MeV 1~2MeV N.Fukuda, TN et al., PRC70, 054606 (2004) TN et al.,PLB 331,296(1994) dB(E1) dE x S n =504keV core n dB(E1) dE x  exp(iqr)| rY 1 m |  gs  | 2 Z A Direct Breakup

5. |  gs (1/2 + )  =  | 10 Be(0 + )  s 1/2  | 10 Be(2 + )  d 5/2      : Spectroscopic factor dB(E1) dE x  exp(iqr)| rY 1 m |  gs  | 2 Z A   -S n  ~   |exp(-r/ )/r| 2 Fourier Transform   = 0.72  c.f.   = 0.77 10 Be(d,p) 11 Be  2 = 0.61(5) R.Palit PRC68,034318(2003)(GSI) Low-lying E1 Strength Halo State Spectroscopic Significance---1n Halo nucleus 11 Be(g.s.) Exclusively Sensitive to the Halo State B(E1) @E~1MeV  exp(iqr)| rY 1 m | s 1/2  | 2 Z A Halo State Direct Breakup Mechanism N.Fukuda, TN et al., PRC70, 054606 (2004)

6. One neutron halo nucleus vs. Two neutron halo nucleus 9Li9Li n n 10 Be n Motion between core and 1 valence neutron Motion between 1.Core and neutron 2.Core and neutron 3.Two valence neutrons (neutron-neutron correlations) S 2n =300 keV S n =504 keV

7. RIKEN @ 43MeV/nucleon PLB348 (1995) 29. MSU@ 28MeV/nucleon PRL 70 (1993) 730. Coulomb Dissocitaion of 11 Li GSI @280MeV/nucleon NPA 619 (1997) 151. dB(E1)/dEx Should be Compared !

8. Coulomb Dissocitaion of 11 Li (Summary of Previous Results) RIKEN @ 43MeV/nucleon PLB348 (1995) 29. GSI @280MeV/nucleon NPA 619 (1997) 151. MSU@ 28MeV/nucleon PRL 70 (1993) 730. PRC 48(1993) 118.

9. 11 Li 9 Li n n Experimental Setup @RIPS at RIKEN Pb Target NEUT HOD BOMAG DC DALI 70MeV/nucleon

10. Examine Different Wall Events t1t1 t2t2 11 22  12 Condition: Almost no bias E th =6MeVee to avoid any gamma related events Elimination of Cross-Talk events

11. Coulomb Dissociation Spectrum of 11 Li Preliminary 11 Li 9 Li+n+n

12. Angular Distribution E1 Strength Distribution

13. =E x (E rel +0.2MeV) Uncorrelated pair Correlated Pair Independent Particle Model ( 10 Li+n) H.Esbensen et al.,NPA542(1992)310. “Soft dipole excitations in 11 Li” Correlation? (E rel ~0.2MeV) (E rel ~0.7MeV)

14. Correlation? B(E1) sum rule (H.Esbensen et al.,NPA542(1992)310.) Experimental value c.f. Shimoura et al.,PLB348(1995)29. Correlated pair 1.57 e 2 fm 2 ~60deg Independent Particle 1.07e 2 fm 2 90deg Preliminary

15. Experimental Result E(9Li-n) 1MeV Simulation (Phase-space decay) E(9Li-n) 1MeV Correlation? Preliminary

16. Summary Coulomb Dissociation----- Low-lying B(E1) Strength ---- Sensitive to Halo s-wave neutron x Core( 0 + ) Powerful Spectroscopic Tool 11 Be(1n halo)+Pb Data 11 Li(2n halo)+Pb Data Low-lying B(E1) Strength Could be used to see the nn correlation & 9 Li-n correlation in 11 Li (E1 Non-energy weighted sum rule) Strong B(E1) at very low excitation energy E( 9 Li-n) - E( 9 Li-n) 2 dimensional Plot Strong Correlations Theoretical interpretation is necessary   = 0.72  N.Fukuda, T.N. et al., PRC70, 054606 (2004)