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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. T.Nakamura, A.M. Vinodkumar , T.Sugimoto,
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Coulomb breakup of the two-neutron halo nucleus 11Li Takashi Nakamura Tokyo Institute of Technology International Conference on Finite Fermionic SystemsNilsson Model 50 YearsJune 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
dB(E1) dEx Introduction Coulomb Breakup Invariant Mass 11Li 11Li* 9Li n g n ~70MeV/nucleon (b ~0.4c) High-Z Target (Pb) Equivalent Photon Method dsCD 16p3 = NE1(Ex) dEx 9hc Cross section = (Photon Number)x(Transition Probability)
dB(E1) Direct Breakup dEx core n dB(E1) Z µ| á exp(iqr)| rY1m|Fgsñ |2 dEx A 11Be – One neutron Halo Case 1~2MeV Sn=504keV Ex 10~20MeV N.Fukuda, TN et al., PRC70, 054606 (2004) TN et al.,PLB 331,296(1994)
Spectroscopic Significance---1n Halo nucleus Direct Breakup Mechanism r ~ a2 |exp(-r/l)/r|2 dB(E1) Z µ| á exp(iqr)| rY1m|Fgsñ |2 dEx A Z -Sn | á exp(iqr)| rY1m|s1/2ñ |2 a2 µ Fourier Transform A Low-lying E1 Strength Halo State B(E1) @E~1MeV Exclusively Sensitive to the Halo State | Fgs (1/2+)ñ = a |10Be(0+)Ä2s1/2 ñ + b|10Be(2+)Ä1d5/2 ñ 11Be(g.s.) Halo State a2 = 0.72±0.04 N.Fukuda, TN et al., PRC70, 054606 (2004) a2,b2: Spectroscopic factor c.f. a2 = 0.77 10Be(d,p)11Be a2 = 0.61(5) R.Palit PRC68,034318(2003)(GSI)
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)
Coulomb Dissocitaion of 11Li GSI @280MeV/nucleon NPA 619 (1997) 151. RIKEN @ 43MeV/nucleon PLB348 (1995) 29. dB(E1)/dEx Should be Compared ! MSU@ 28MeV/nucleon PRL 70 (1993) 730.
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.
Experimental Setup NEUT @RIPS at RIKEN n n Pb Target 9Li HOD DC DALI 11Li 70MeV/nucleon BOMAG
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
Coulomb Dissociation Spectrum of 11Li 9Li+n+n 11Li Preliminary
Angular Distribution E1 Strength Distribution
Correlation? Independent Particle Model (10Li+n) Uncorrelated pair Correlated Pair (Erel~0.7MeV) (Erel~0.2MeV) =Ex (Erel+0.2MeV) H.Esbensen et al.,NPA542(1992)310. “Soft dipole excitations in 11Li”
Correlation? B(E1) sum rule(H.Esbensen et al.,NPA542(1992)310.) Experimental value Preliminary Correlated pair 1.57 e2fm2 ~60deg Independent Particle 1.07e2fm2 90deg c.f. Shimoura et al.,PLB348(1995)29.
Simulation (Phase-space decay) 1MeV E(9Li-n) 1MeV E(9Li-n) Correlation? Experimental Result 1MeV E(9Li-n) 1MeV E(9Li-n) Preliminary
Summary 11Be(1n halo)+Pb Data Coulomb Dissociation----- Low-lying B(E1) Strength ----Sensitive to Halo s-wave neutron x Core( 0+) a2 = 0.72±0.04 Powerful Spectroscopic Tool N.Fukuda, T.N. et al., PRC70, 054606 (2004) 11Li(2n halo)+Pb Data Strong B(E1) at very low excitation energy Low-lying B(E1) Strength Could be used to see the nn correlation & 9Li-n correlation in 11Li (E1 Non-energy weighted sum rule) Strong Correlations Theoretical interpretation is necessary E(9Li-n) - E(9Li-n) 2 dimensional Plot