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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
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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
Collaborators
Coulomb Breakup of 11LiSubmitted to Phys.Rev.Lett.
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Invariant Mass Method (unbound excited states)
RadioactiveIon beam
BreakupKinematicFocusing
Well-defined Energy by Invariant Mass
ThickTarget
Ex
12Be vs. 14Be
12Be0+
2+0+
1-
2.24
2.70 MeV
2.10
14Be Drip line
11Be+n3.169 MeV
0+
1.264 MeV
? 2+
12Be+2nBound RegionInbeam spectroscopy
Unbound RegionInvariant massspectroscopy
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14Be + 12C 12Be + n + n + 12C
Eex = S2n + Erel = 1.56 0.13 MeV
Erel (MeV)
d/d
Ere
l(mb/
MeV
)
T.Sugimoto, TN et al., (2006)
1.56MeV
N=8MagicityLoss
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HHe
LiBeBC
NO
FNe
Neutron Dripline
N=8
N=20
11Be19C
N
Z Neutron halosStudied by InvariantMass Method by our group
11Li
11Li11Be
2n halo nucleus1n halo nucleus
Neutron Halo Nuclei– Nuclei at the stability limit
9Li
n
n10Ben
Sn=504 keV S2n=300 keV
14Be
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11Li
High-Z Target (Pb)
9Li
n
= NE1(Ex)dB(E1)dEx
dCD
dEx 9hc163
Cross section = (Photon Number)xTransition Probability)
Invariant Mass
Equivalent Photon Method
relx , EE
)Li(),(),( 9PnPnP
11Li*
n
Coulomb Breakup of 11Li
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11Be : E1 Response of one-neutron Halo
Ex10~20MeV
1~2MeV
N.Fukuda, TN et al., PRC70, 054606 (2004) TN et al.,PLB 331,296(1994)
core n
dB(E1)dEx
)W.u06.029.3(
fm06.005.1)1( 22
eEB
11Be
dB(E1)dEx
exp(iqr)| rY1m|gs
|2
ZA
-Sn
~ |exp(-r/)/r|2
Fourier Transform
Low-lying E1 Strength Halo State
exp(iqr)| rY1m|s1/2 |2Z
A
Direct Breakup Mechanism
Sn=504keV
= 0.72
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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
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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.
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• RIPS@RIKEN• Primary Beam
18O 100 AMeV• Projectile Frag
mentation• Secondary Bea
m11Li ~70 AMeV~20 kcps
RIKENProjectile-fragment Separator
18O 100 AMeV
11Li ~70 AMeV
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11Li
9Li
nn
Experimental Setup@RIPS at RIKEN
Pb Target
NEUT
HOD
BOMAG
DC
DALI
70MeV/nucleon
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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
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Coulomb Dissociation Spectrum of 11Li
MeV3for
b.)(28.0.)(05.034.2
rel
E
syststat
Angular Distribution
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Calculation:H.Esbensen et al.,NPA542(1992)310. Private Communication
“Soft dipole excitations in 11Li”
Present Result
Comparison with the 3-bodytheorykeV3002 nS
= NE1(Ex)dB(E1)dEx
dCD
dEx 9hc163
B(E1) Distribution
MeV3
18.042.1)1(
rel
22
E
fmeEB
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Non-energy weightedE1 Cluster Sum Rule
22
2
212
22
1
2
0
3
)(24
3)1()1(
nc
xx
rA
Ze
rrrrA
ZedE
dE
EdBEB
r1
r2 n
9Li
rc-2n
fm32.001.5
)22(78.1
)3MeV(18.042.1)1(
2
2
22
rel22
ncr
fme
EfmeEB
(Extrapolated cluster strength)
~70% larger than non-correlatedstrength 021 rr
deg50~12
H.Esbensen et al.,NPA542(1992)310.
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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?
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Summary
11Li(2n halo)+Pb (Coulomb Breakup)
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 2218.042.1)1( fmeEB
c.f. B(E1)=1.05(6) e2fm2 for 11Be
Invariant Mass Spectroscopy ----Powerful Spectroscopic tool