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Invariant-mass spectroscopy of neutron halo nuclei

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. Coulomb Breakup of 11 Li Submitted to Phys.Rev.Lett. Collaborators. T.Nakamura, A.M. Vinodkumar, T.Sugimoto, N.Fukuda, M.Miura, Y.Kondo, N.Aoi, N.Imai,

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Invariant-mass spectroscopy of neutron halo nuclei

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  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. Coulomb Breakup of 11Li Submitted to Phys.Rev.Lett. Collaborators 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. Invariant Mass Method (unbound excited states) Breakup Ex Kinematic Focusing Radioactive Ion beam Well-defined Energy by Invariant Mass Thick Target 12Be vs. 14Be 3.169 MeV Unbound Region Invariant massspectroscopy 11Be+n 2.70 MeV 1- 2.24 0+ 2.10 ? 2+ 2+ 1.264 MeV Bound Region Inbeam g spectroscopy 12Be+2n 0+ 0+ 14Be Drip line 12Be

  4. 1.56MeV 14Be + 12C  12Be + n + n + 12C N=8 Magicity Loss Eex = S2n + Erel = 1.56  0.13 MeV T.Sugimoto, TN et al., (2006) ds/dErel(mb/MeV) Erel (MeV)

  5. Neutron Halo Nuclei– Nuclei at the stability limit Ne F O N=20 N C Neutron halos Studied by Invariant Mass Method by our group B Z Be Neutron Dripline Li He H N=8 11Li 19C N 11Be 14Be 2n halo nucleus 1n halo nucleus n 9Li 11Li n 10Be 11Be n Sn=504 keV S2n=300 keV

  6. dB(E1) dEx Coulomb Breakup of 11Li Invariant Mass 11Li 11Li* 9Li n g n High-Z Target (Pb) Equivalent Photon Method dsCD 16p3 = NE1(Ex) dEx 9hc Cross section = (Photon Number)x(Transition Probability)

  7. dB(E1) dEx 11Be : E1 Response of one-neutron Halo 1~2MeV Ex 10~20MeV 11Be Sn=504keV N.Fukuda, TN et al., PRC70, 054606 (2004) TN et al.,PLB 331,296(1994) Direct Breakup Mechanism core n r ~ a2 |exp(-r/l)/r|2 Low-lying E1 Strength Halo State dB(E1) Z µ| á exp(iqr)| rY1m|Fgsñ |2 dEx A -Sn Fourier Transform Z a2 µ | á exp(iqr)| rY1m|s1/2ñ |2 A a2 = 0.72±0.04

  8. One neutron halo nucleus vs. Two neutron halo nucleus n n 9Li 10Be S2n=300 keV Sn=504 keV n Motion between core and 1 valence neutron • Motion between • Core and neutron • Core and neutron • Two valence neutrons • (neutron-neutron correlations)

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

  10. RIKENProjectile-fragment Separator 11Li ~70 AMeV 18O 100 AMeV • RIPS@RIKEN • Primary Beam18O 100 AMeV • Projectile Fragmentation • Secondary Beam11Li ~70 AMeV~20 kcps

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

  12. Elimination of Cross-Talk events Examine Different Wall Events Almost no bias Condition: t1 b1 b12 b2 t2 Eth=6MeVee to avoid any gamma related events

  13. Coulomb Dissociation Spectrum of 11Li Angular Distribution

  14. dB(E1) dEx dsCD 16p3 = NE1(Ex) dEx 9hc B(E1) Distribution Comparison with the 3-body theory Present Result Calculation: H.Esbensen et al.,NPA542(1992)310. Private Communication “Soft dipole excitations in 11Li”

  15. Non-energy weightedE1 Cluster Sum Rule H.Esbensen et al.,NPA542(1992)310. rc-2n r2 n r1 9Li (Extrapolated cluster strength) ~70% larger than non-correlated strength

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

  17. Summary Invariant Mass Spectroscopy ----Powerful Spectroscopic tool 11Li(2n halo)+Pb (Coulomb Breakup) Strong B(E1) at very low excitation energy c.f. B(E1)=1.05(6) e2fm2 for 11Be Low-lying B(E1) Strength Could be used to see the nn correlation & 9Li-n correlation in 11Li (E1 Non-energy weighted sum rule)

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