Coulomb breakup of the two-neutron halo nucleus 11Li Takashi Nakamura Tokyo Institute of Technology International Conference on Finite Fermionic Systems Nilsson Model 50 Years June 14-18 2005, Lund, Sweden 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 Introduction Li 11 Coulomb Breakup 11
~70MeV/nucleon (~0.4c) Li* 9 P(n), P (n), P ( Li) Invariant Mass E x , E rel 9 Li n n High-Z Target (Pb)
Equivalent Photon Method dCD 163 dB(E1) = N (E ) dEx 9hc E1 x dEx Cross section = (Photon Number)xTransition Probability) 11 Be One neutron Halo Case 1~2MeV dB(E1) Sn=504keV dEx Ex
10~20MeV B ( E1) 1.05 0.06 e 2 fm 2 (3.29 0.06 W.u ) Direct Breakup core n dB(E1) exp(iqr)| Z rY1 | m gs N.Fukuda, TN et al., PRC70, 054606 (2004) dEx A TN et al.,PLB 331,296(1994) |2 r / gs
e r B ( E1) 1 / S n 8 E x ( peak ) S n 5 Spectroscopic Significance---1n Halo nucleus Direct Breakup Mechanism dB(E1) exp(iqr)| Z rY1 | m gs dEx A |2 Z rY1 |s |2Fourier exp(iqr)|
m 1/2 A Transform Low-lying E1 Strength ~ |exp(-r/)/r|2 -Sn Halo State B(E1) @E~1MeV Exclusively Sensitive to the Halo State | gs (1/2+) = |10Be(0+)s1/2 |10Be(2+)d5/2 11 Halo State Be(g.s.) = 0.72 N.Fukuda, TN et al., PRC70, 054606 (2004) : Spectroscopic factor c.f. = 0.77 10Be(d,p)11Be 2 = 0.61(5) R.Palit PRC68,034318(2003)(GSI) One neutron halo nucleus vs. Two neutron halo nucleus
n 10 n Be Sn=504 keV Motion between core and 1 valence neutron 9 Li n S2n=300 keV Motion between 1. Core and neutron 2. Core and neutron
3. Two valence neutrons (neutron-neutron correlations) Coulomb Dissocitaion of 11Li GSI @280MeV/nucleon NPA 619 (1997) 151. RIKEN @ 43MeV/nucleon PLB348 (1995) 29. [email protected] 28MeV/nucleon PRL 70 (1993) 730. dB(E1)/dEx Should be Compared ! Coulomb Dissocitaion of 11Li (Summary of Previous Results) [email protected] 28MeV/nucleon PRL 70 (1993) 730. PRC 48(1993) 118.
RIKEN @ 43MeV/nucleon PLB348 (1995) 29. GSI @280MeV/nucleon NPA 619 (1997) 151. Experimental Setup NEUT @RIPS at RIKEN n n Pb Target 9 Li HOD DC
DALI 11 Li 70MeV/nucleon BOMAG Elimination of Cross-Talk events Examine Different Wall Events Condition: 1 12 Almost no bias t1 1 12 2
Eth=6MeVee to avoid any gamma related events t2 Coulomb Dissociation Spectrum of 11Li Erel Ex 11 Li S 2n Li+n+n 9 2.86(8) b Preliminary
Angular Distribution E1 Strength Distribution Independent Correlation? Particle Model Uncorrelated Correlated (10Li+n) pair Pair (Erel~0.7MeV) (Erel~0.2MeV) =Ex (Erel+0.2MeV) H.Esbensen et al.,NPA542(1992)310. Soft dipole excitations in 11Li B(E1) sum rule Correlation?
(H.Esbensen et al.,NPA542(1992)310.) 2 dB( E1) 3 Ze 2 2 B( E1) dEx r1 r2 2(r1 r2 ) 0 dEx 4 A r 2 5.1 fm Experimental value B( E1) 1.6 0.1e 2 fm 2 ( E rel 3 MeV) Preliminary
Correlated pair 1.57 e2fm2 ~60deg Independent Particle 1.07e2fm2 90deg c.f. Shimoura et al.,PLB348(1995)29. r 2 5.1 fm Simulation (Phase-space decay) E(9Li-n) 1MeV Experimental Result E(9Li-n) 1MeV Correlation? E(9Li-n)
Preliminary 1MeV E(9Li-n) 1MeV Summary 11 Be(1n halo)+Pb Data Coulomb Dissociation----Low-lying B(E1) Strength ----Sensitive to Halo s-wave neutron x Core( 0+) Powerful Spectroscopic Tool = 0.72 N.Fukuda, T.N. et al., PRC70, 054606 (2004)
11 Li(2n halo)+Pb Data Strong B(E1) at very low excitation energy B ( E1) 1.6 0.1e 2 fm 2 ow-lying B(E1) Strength Could be used to see the nn correlation & 9Li-n correlation in 11Li (E1 Non-energy weighted sum rule) E(9Li-n) - E(9Li-n) 2 dimensional Plot Strong Correlations Theoretical interpretation is necessary
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