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Invariant-mass spectroscopy of neutron halo nuclei Takashi Nakamura 中村隆司 Tokyo Institute of Technology 東京工業大学 中日 NP 06, Shanghai.

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Presentation on theme: "Invariant-mass spectroscopy of neutron halo nuclei Takashi Nakamura 中村隆司 Tokyo Institute of Technology 東京工業大学 中日 NP 06, Shanghai."— Presentation transcript:

1 Invariant-mass spectroscopy of neutron halo nuclei Takashi Nakamura 中村隆司 Tokyo Institute of Technology 東京工業大学 中日 NP 06, Shanghai

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 Collaborators Coulomb Breakup of 11 Li Submitted to Phys.Rev.Lett.

3 Invariant Mass Method (unbound excited states) Radioactive Ion beam Breakup Kinematic Focusing Well-defined Energy by Invariant Mass Thick Target Ex 12 Be vs. 14 Be 12 Be MeV Be Drip line 11 Be+n MeV MeV ? Be+2n Bound Region Inbeam  spectroscopy Unbound Region Invariant mass  spectroscopy

4 14 Be + 12 C  12 Be + n + n + 12 C E ex = S 2n + E rel = 1.56  0.13 MeV E rel (MeV) d  /dE rel (mb/MeV) T.Sugimoto, TN et al., (2006) 1.56MeV N=8 Magicity Loss

5 H He Li Be B C N O F Ne Neutron Dripline N =8 N =20 11 Be 19 C N Z Neutron halos Studied by Invariant Mass Method by our group 11 Li 11 Be 2n halo nucleus 1n halo nucleus Neutron Halo Nuclei– Nuclei at the stability limit 9Li9Li n n 10 Be n S n =504 keV S 2n =300 keV 14 Be

6 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 Equivalent Photon Method 11 Li* n Coulomb Breakup of 11 Li

7 11 Be : E1 Response of one-neutron Halo ExEx 10~20MeV 1~2MeV N.Fukuda, TN et al., PRC70, (2004) TN et al.,PLB 331,296(1994) core n dB(E1) dE x 11 Be dB(E1) dE x  exp(iqr)| rY 1 m |  gs  | 2 Z A   -S n  ~   |exp(-r/ )/r| 2 Fourier Transform Low-lying E1 Strength Halo State  exp(iqr)| rY 1 m | s 1/2  | 2 Z A Direct Breakup Mechanism S n =504keV   = 0.72 

8 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

9 Coulomb Dissocitaion of 11 Li (Summary of Previous Results) 43MeV/nucleon PLB348 (1995) 29. NPA 619 (1997) MeV/nucleon PRL 70 (1993) 730. PRC 48(1993) 118.

10 Primary Beam 18 O 100 AMeV Projectile Fragmentation Secondary Beam 11 Li ~70 AMeV ~20 kcps RIKEN Projectile-fragment Separator 18 O 100 AMeV 11 Li ~70 AMeV

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

12 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

13 Coulomb Dissociation Spectrum of 11 Li Angular Distribution

14 Calculation: H.Esbensen et al.,NPA542(1992)310. Private Communication “Soft dipole excitations in 11 Li” Present Result Comparison with the 3-body theory = N E1 (E x ) dB(E1) dE x d  CD dE x 9hc 16  3 B(E1) Distribution

15 Non-energy weighted E1 Cluster Sum Rule r1r1 r2r2 n 9 Li r c-2n (Extrapolated cluster strength) ~70% larger than non-correlated strength H.Esbensen et al.,NPA542(1992)310.

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

17 Summary 11 Li(2n halo)+Pb (Coulomb Breakup) 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 c.f. B(E1)=1.05(6) e 2 fm 2 for 11 Be Invariant Mass Spectroscopy ----Powerful Spectroscopic tool


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