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

Coulomb Breakup

11Li

High-Z Target (Pb)

9Li

n

= NE1(Ex)dB(E1)dEx

dCD

dEx 9hc163

Cross section = (Photon Number)xTransition Probability)

Invariant Mass

~70MeV/nucleon(~0.4c)

Equivalent Photon Method

relx , EE

)Li(),(),( 9PnPnP

Introduction

11Li*

n

11Be – One neutron Halo Case

Ex10~20MeV

1~2MeV

N.Fukuda, TN et al., PRC70, 054606 (2004) TN et al.,PLB 331,296(1994)

dB(E1)dEx

Sn=504keV

)W.u06.029.3(

fm06.005.1)1( 22

eEB

core n

dB(E1)dEx

exp(iqr)| rY1m|gs

|2

ZA

Direct Breakup

nSEB /1)1( nx SpeakE5

8)(

r

e r

gs

/

| gs (1/2+) = |10Be(0+)s1/2 |10Be(2+)d5/2

: Spectroscopic factor

dB(E1)dEx

exp(iqr)| rY1m|gs

|2

ZA

-Sn

~ |exp(-r/)/r|2

Fourier Transform

= 0.72

c.f. = 0.77 10Be(d,p)11Be

2 = 0.61(5) R.Palit PRC68,034318(2003)(GSI)

Low-lying E1 Strength Halo State

Spectroscopic Significance---1n Halo nucleus

11Be(g.s.)

Exclusively Sensitive to the Halo StateB(E1) @E~1MeV

exp(iqr)| rY1m|s1/2 |2Z

A

Halo State

Direct Breakup Mechanism

N.Fukuda, TN et al., PRC70, 054606 (2004)

One neutron halo nucleus vs. Two neutron halo nucleus

9Li

n

n10Ben

Motion between core and 1 valence neutron

Motion between 1. Core and neutron2. Core and neutron3. Two valence neutrons (neutron-neutron correlations)

S2n=300 keVSn=504 keV

RIKEN @ 43MeV/nucleonPLB348 (1995) 29.

MSU@ 28MeV/nucleon

PRL 70 (1993) 730.

Coulomb Dissocitaion of 11Li

GSI @280MeV/nucleonNPA 619 (1997) 151.

dB(E1)/dExShould beCompared !

Coulomb Dissocitaion of 11Li (Summary of Previous Results)

RIKEN @ 43MeV/nucleonPLB348 (1995) 29.

GSI @280MeV/nucleonNPA 619 (1997) 151.

MSU@ 28MeV/nucleonPRL 70 (1993) 730.PRC 48(1993) 118.

11Li

9Li

nn

Experimental Setup@RIPS at RIKEN

Pb Target

NEUT

HOD

BOMAG

DC

DALI

70MeV/nucleon

Examine Different Wall Events

t1

t2

1

2

12

Condition: 121 Almost no bias

Eth=6MeVee to avoid any gamma related events

Elimination of Cross-Talk events

Coulomb Dissociation Spectrum of 11Li

Preliminary

b)8(86.2

xErelE

nS211Li

9Li+n+n

Angular Distribution E1 Strength Distribution

=Ex (Erel+0.2MeV)

Uncorrelated pair

Correlated Pair

IndependentParticle Model(10Li+n)

H.Esbensen et al.,NPA542(1992)310.

“Soft dipole excitations in 11Li”

Correlation?

(Erel~0.2MeV)(Erel~0.7MeV)

Correlation?B(E1) sum rule (H.Esbensen et al.,NPA542(1992)310.)

)(24

3)1()1( 21

22

21

2

0rrrr

A

ZedE

dE

EdBEB x

x

Experimental value

)MeV3(

1.06.1)1(

rel

22

E

fmeEB

c.f. Shimoura et al.,PLB348(1995)29.

Correlated pair 1.57 e2fm2 ~60deg

Independent Particle 1.07e2fm2 90deg

fm1.52 r

Preliminary

fm1.52 r

Experimental Result

E(9Li-n)

E(9

Li-n

)

1MeV

1MeV

Simulation (Phase-space decay)

E(9Li-n)

E(9

Li-n

)

1MeV

1MeV

Correlation?

Preliminary

Summary

Coulomb Dissociation-----

Low-lying B(E1) Strength ----Sensitive to Halo s-wave neutron x Core( 0+)

Powerful Spectroscopic Tool

11Be(1n halo)+Pb Data

11Li(2n halo)+Pb Data

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 B(E1) at very low excitation energy 221.06.1)1( fmeEB

E(9Li-n) - E(9Li-n) 2 dimensional Plot Strong CorrelationsTheoretical interpretation is necessary

= 0.72N.Fukuda, T.N. et al., PRC70, 054606 (2004)