Coulomb Breakup of Halo Nuclei

T. Nakamura

Tokyo Institute of Technology

Coulomb Breakup of 11Li1

Contents

T. Nakamura, A.M.Vinodkumar et al., Phys. Rev. Lett. 96, 252502 (2006)

2

3 SAMURAI/NEBULA Project at RIKEN RIBF

Inclusive Coulomb Breakup of 31Ne and 22C :

Dayone experiments at RIBF

0 Introduction

Introduction

•Soft Dipole Excitation

—Structureless E1 Continuum due to Halo Structure

Enhancement of E1 Strength at Low Excitation Energies

Ex

dB(E1)dEx

10~20MeV

GDR~1MeV Soft E1

Unique properties

for Neutron Halo Nuclei

Questions

• Nuclear Halo --- Universal?

• How is nuclear structure at the drip line characterized?

Coulomb Breakup

• One neutron halo

• Two neutron halo

How B(E1) can be related to halo structure?

Di-neutron Correlation?

Coulomb Breakup of 11Li 1

T. Nakamura, A.M.Vinodkumar et al.,

Phys. Rev. Lett. 96, 252502 (2006).

HHe

LiBeBC

NO

FNe

N=8

N=20

11Li 14Be

19C

17C

11Li

High-Z Target

(Pb)

9Li

ng

= NE1(Ex)dB(E1)dEx

dsCD

dEx 9hc

16p3

Cross section = (Photon Number)x(Transition Probability)

Invariant Mass

Equivalent Photon Method

relx , EE

)Li(),(),( 9PnPnP

11Li*

n

Coulomb Breakup

Examine Different Wall Events

t1

t2

b1

b2

b12

Condition: 121 bb Almost no bias

Elimination of Cross-Talk events

High detection sensitivity

even at Erel~0MeV (q~0)

q

11Li

NEUT

Wall 1

NEUT

Wall 2

Precise measurement

of B(E1) distribution of 11Li

Experimental Results

H.Esbensen and G.F. Bertsch

NPA542,310 (1992).

Comparison with

3-body Theory-1

Calculation

H.Esbensen et al.,

PRC76, 024302 (2007)

TN et al. PRL96,252502(2006).

W.u)6(5.4

)3MeV(18.042.1)1( rel

22

EfmeEB

Non-energy weighted

E1 Cluster Sum Rule

2

2

2

21

2

2

2

1

2

0

3

)(24

3)1()1(

nc

x

x

rA

Ze

rrrrA

ZedE

dE

EdBEB

p

p

r1

r2 n

9Li

rc-2n

fm32.001.5

)22(78.1

)3MeV(18.042.1)1(

2

2

22

rel

22

ncr

fme

EfmeEB

(Extrapolated value)

~70% larger than non-correlated

strength ( 021 rr

deg48 14

1812

q

n

Comparison with 3-body theory-2

Myo et al.,PRC76,024305 (2007).

Core polarization

(Tensor correlation+Pauli Principle)

P(S2)~ 40% fm38.52

2 ncr deg6512 q

Both Charge distribution & B(E1) are reproduced.

O(E1)|11Li(gs)>

?

9Li

n

n

2n Correlations can be studied by 3-body decay of 11Li*?

)(9 LiPcm

)(nPcm

)(nPcm

--Kinematically complete measurement

Experimental Result

E(9Li-n)

E(9

Li-n)

1M

eV

Further Correlation?E(9Li-n)

n

9Li

E(9Li-n)

1MeV

Simulation (Phase Space)

E(9Li-n)

n

34.2q

10Li s-wave

Virtual state

p-wave?

...)()()Li()Li(|)1(

...)()Li()()Li()Li(

1

2/1

1

2/1gs

9

gs

11

2

2/1gs

92

2/1gs

9

gs

11

psEO

ps

g

b

E(9Li-n)

E(9

Li-n)

34.2q

2 Inclusive Coulomb Breakup

of 31Ne and 22C

@ RIKEN RI BEAM FACTORY

As an experiment for

Day-one 48Ca beam campaign,

December 2008

ZDS

48Ca 345MeV/nucleon ~100pnA

SRC

BIGRIPSIRC

FRC

RRC

RIKEN RI Beam Factory (RIBF) Completed in 2007

World Largest RI-beam facility

HHe

LiBeBC

NO

FNe

NaMgAlSi

PS

ClAr

KCa

N=8N=2

Drip Line

11Li

11Be 19C

20C

22C 31Ne

Island of Inversion

48Ca

345MeV/u31Ne ~230MeV/u22,20,19C ~250MeV/u

Pb,C tgt

TOF Br, DE

Eth

x

x

xE dEdE

EdBEN

cE

)1()(

9

16)1( 1

3

ps

Inclusive Coulomb Breakup

31Ne+Pb30Ne+X22C+Pb20C+X

TOF,DEBr@ZDS

22C

19B17B

20C19C

23N22N

TOF (ns) (F3-F7) ~A/Z

DE

(F7PL)

３ SAMURAI / NEBULA PROJECT

@ RIKEN RI BEAM FACTORY

ZDS

48Ca 345MeV/nucleon ~100pnA

SRC

BIGRIPSIRC

FRC

RRC

RIKEN RI Beam Factory (RIBF)

SAMURAI

To let neutron(s) pass

through the gap

Sweep Beam and

Charged Fragments

Good Mass Resolution

for PID @ A~100

SAMURAISuperconducting Analyser for MUlti-particles from RAdio-Isotope Beam

Bending Power

BL=7Tm (B=3Tesla, 60deg bending)

2008-2011 1.5GJPY~16MUSD~13MEuro

+NEBULA(NEutron Detection

System for Breakup of

Unstable Nuclei with

Large Acceptance)

Superconducting

Magnet

126

8228

Physics of Neutron-rich Nuclei

via Breakup Reactions (@SAMURAI/NEBULA)

28

82

20

8

2

50

20

50

82

Giant Halos? 2n, 4n-correlation?

New Cluster/Molecular States?

States beyond drip-lines? (4n,28O, and more)

Drip-Line Physics

Structures and reactions

of r-process nucleiGiant and Pigmy resonances

of Neutron-skin nuclei

Neutron Star/Nuclear Matter

Summary

• Strong B(E1) at very low excitation energy

• neutron-neutron spatial correlation from E1 sum rule

qnn~50deg

•3body correlation in the decay of the dipole halo state

)keV300(18.042.1)1( 2

22 nSfmeEB

Coulomb Breakup of 11Li and two-neutron correlationT. Nakamura, A.M.Vinodkumar et al., Phys. Rev. Lett. 96, 252502 (2006).

1

3 SAMURAI/NEBULA Project

2 Inclusive Coulomb Breakup of 22C and 31Ne

Accumulated about ~1000 1n removal

events

Promising results

Collaborators

T.Nakamura, A.M.Vinodkuar, T.Sugimoto, Y.Kondo, N. Aoi, H. Baba, D. Bazin,

N. Fukuda, T. Gomi, H. Hasegawa, N. Imai, M. Ishihara, T.Kobayashi, T. Kubo,

M. Miura, T. Motobayashi, H. Otsu, A.Saito, H.Sakurai, S. Shimoura, K.

Watanabe, Y.X. Watanabe, T. Yakushiji, Y. Yanagisawa, K. Yoneda

Coulomb Breakup of 11Li ( PRL96,252502(2006))

Inclusive Coulomb Breakup of 31Ne and 22C as

an experiment in RIBF DayOne Campaign

T.Nakamura, N.Kobayashi(Duracell), Y.Satou, Y.Kondo, K.Tanaka, Y.Kawada,

N.Tanaka, S.Deguchi,N.Aoi,K.Yoneda,H.Baba, S.Takeuchi, T.Ohnishi,T.Kubo,

A.Saito, S.Shimoura, H.Sakurai, M.Ishihara, N.Orr, M.Takechi,T.Sumikama,

Y.Togano, E.Takeshita, H.Takeda,A.Yoshida,K.Yoshida,K.Kusaka,

Y.Yoshinaga,K.Miyashita

東工大物理GCOE 研究員募集中（１月２７日締切）www.phys.titech.ac.jp を参照下さい。