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分解反応で探るダイニュートロン相関
中村隆司
東京工業大学・理工学研究科
クラスターガス状態探索のための研究戦略会議@RCNP 2011.9.7-9.8
3
Contents
Inclusive Coulomb Breakup of 22C :
1 Dineutron相関とは?
4 今後の展望
2 Dineutron相関を見るプローブ
クーロン分解、核力分解
Dineutron相関とは
A.B.Migdal “Two interacting particles in a potential well”
Sov.J. Nucl. Phys.16, 238 (1973).
n n Unbound
(Virtual State 1S0) n n
Bound nn system
In the surface of
nucleus
現代版Dineutron
BCS的対相関(長距離相関) Dineutron的対相関(BEC-ボソン凝縮的)(短距離相関)
n n n
n
Dineutron的相関
低密度下でおこる
r/r0~10-4~-5
M.Matsuo et al.
PRC73,044309(2006).
弱束縛系のDineutron -I
K.Hagino, H.Sagawa, J.Carbonell, P.Schuck
PRL99,022506 (2007).
T.Myo et al.,PRC76, 024305(2007). Esbensen Bertsch, NPA542, 310 (1992).
n
n
Dineutron configuration
n
n
Cigar configuration
M.V.Zhukov, D.V. Fedorov, B.V.Danilin,
J.S. Vaagen, J.M. Bang, NPA92,177(1992)
r1
r2 n
9Li
rc-2n
弱束縛系のDineutron -II Dineutron 相関: a|(1p)2> +b |(2s)2> + g|(1d)2> + ….
異なるParityのpairingの重ね合わせDineutron correlation
r1
r2 n
9Li
rc-2n
2
12
22
12
222
12
22
12 )1(cos)0(2)0(cos)0()1(cos)1(cos spppss abba
2
12
2 )1(cos)0(2 sp ab
2211 )0()1()Li( psCore ba
Simple two-neutron shell model
Melting of s(+ parity) and p(-parity) orbitals
90,0cos 1212 If only (1s)2 or (0p)2
%5022 ba deg5512
Correlation なし
If (1s)2 (0p)2 mixed
(N.B. Phase, 動径波動関数にも依存)
安定核におけるDineutron?
18O: l=7まで,Ex=30MeVまでの
一粒子レベルを入れた計算
(1d)2+少量(odd parity)2
dineutron相関 @Surface
K.Hagino, H.Sagawa, P.Schuck J.Phys.G: Nucl.Part. Phys. 37, 064040(2010)
18O(16O+n+n) 11Li(9Li+n+n)
本日は2中性子ハロー核のDineutronに特化
K.Hagino, H.Sagawa
Phys. Rev. C 72, 044321 (2005).
“Dineutron” という概念のまとめ
異パリティ2核子状態の重なり
(Dineutron相関の必要条件)
Dineutronの発達
低密度, 弱束縛
n
n 12<<90deg
強い相関を持つ空間的にコンパクトな2中性子系
Dineutron 相関を見るプローブ
-- クーロン分解反応
核力分解反応
2
11Li
High-Z Target
(Pb)
9Li
n g
= NE1(Ex) dB(E1) dEx
dsCB dEx 9hc
16p3
Cross section = (Photon Number)x(Transition Probability)
Invariant Mass
Equivalent Photon Method
relx , EE
)Li(),(),( 9PnPnP
11Li*
v>0.3c
C.A. Bertulani, G. Baur, Phys. Rep. 163,299(1988).
Probe-1: Coulomb Breakup
Photon absorption of a fast projectile
TN et al. PRL96,252502(2006).
W.u)6(5.4
)3MeV(18.042.1)1( rel
22
EfmeEB
Coulomb breakup and soft E1 excitation of 2n halo nuclei
--- Case of 11Li
)(24
3
)1()1(
21
2
2
2
1
2
rrrrA
Ze
dEdE
EdBEB x
x
p
Non-energy weighted E1 Cluster Sum Rule
deg48 14
1812
Soft E1 Excitation(2n-halo)—Sensitive to S2n, l ,
dineutron-like correlation
r1
r2 n
9Li
rc-2n
n
S とp の混合を反映
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)
E(9
Li-
n)
E(9Li-n)
E(9
Li-
n)
1M
eV
1MeV
Full Calc.
FSI
n-9Li 有
nn 無
FSI
n-9Li 無
nn 無
FSI
n-9Li 無
nn 有
K. Hagino, H. Sagawa, TN, S.Shimoura
PRC 80, 031301(R)(2009).
この方法 Final State Interaction にSensitive
G.S.のnn correlation にはInsensitive
Probe-II: Nuclear Breakup (momentum distribution)
14Be 12Be
n
n p target
n 13Be
)Be(14P
)Be(12P)(nP
)Be(13P
)Be(13
P
)Be(12P
)(nP
14Be: 2n Halo Nucleus
Y.Kondo,TN et al.PLB 690, 245 (2010).
70MeV/nucleon
p
s
d
E(13Be):
0.25-0.75MeV p(14Be,12Be+n)
s=103(7)mb (Erel=0-4MeV)
p
d s 12Be+n
13Be 1/2-
5/2+(3/2+)
0.51(1)MeV
2.39(1)MeV
Intruder State(Parity Inversion) E(13Be) (=Erel(
12Be+n)) (MeV) )Be(13
P
3 Inclusive Coulomb Breakup of 22C
@ RIKEN RI BEAM FACTORY
H He
Li Be B C
N O
F Ne
Na Mg Al Si
P S
Cl Ar
K
N=8
N=16
N=20
N=28
N=2
32Mg
Neutron Halo’s along the drip line?
* Estimated value by Audi & Wapstra
2n halo known
4n halo (skin)
1n-halo known
22C (S2n*=0.42(94) MeV)
31Ne (Sn=0.29(1.64) MeV) Jurado et al. PLB649,43(2007).
Island of inversion
19C
Halo?
Ex
(=Eg)
B(E1) (E1 Transition Probability)
~20MeV 1~2MeV
Soft E1 Excitation
(Halo Nuclei)
~0.5--1b <0.1b
Eth
x
x
xE dEdE
EdBEN
cE
)1()(
9
16)1( 1
3
ps
Inclusive Coulomb Breakup
s(E1)
31Ne+Pb30Ne+X
22C+Pb20C+X
Giant Dipole Resonance
(ordinary nuclei)
Halo/Non Halo can be
distintinguished only from
the inclusive cross section !
ZDS
48Ca 345MeV/nucleon
60-150pnA
SRC
BIGRIPS IRC
FRC
RRC
RIKEN RI Beam Factory (RIBF) Completed in 2007
World Largest RI-beam facility
48Ca
345MeV/nucleon
60-150pnA
19C,20C,22C ~240MeV/nucleon 31Ne ~230MeV/nucleon
Pb,C
target
TOF Br, DE
TOF,DE
Br @ZDS
Experiment at BigRIPS & ZDS at RIBF
Particle Identification : 22C20C
22C ~ 6 counts/s
1n(or 2n) removal cross section
Coulomb breakup cross section
6.27.1~
)()()1(
CPbE sss
2n Halo in 22C
1n Halo in 31Ne c.f. 19C (known halo)
Evidence for
Sn(MeV)=0.58(9) 2.93(28) Sn=0.29(1.64)
S2n(MeV)=3.51(24) 0.41(93)
Estimated
From known
B(E1)
TN.PRL83
1112(1999).
1.38(6) b
0.208(14) b
0.92(5)b
Inclusive Coulomb Breakup of 22C and B(E1)
Ex
Assume d function distribution for B(E1) dB/dEx
Ex0
s(E1)=0.92(5) barn (preliminary)
B(E1)~ 1-2e2fm2
• B(E1) distribution of 11Li (TN, PRL2006) s(E1)~1.0 barn (Erel<3MeV)
Strong Soft E1 Excitation as in 11Li
-Possible Prominent 2n-Halo above 11Li (c.f. K.Tanaka et al., PRL 104, 062701(2010))
22C+Pb
a|(2s1/2)2> +b |(2s)2>
74.3% 25.0%
a|(2s1/2)2> +b |(1d3/2)
2> + g|(2p3/2)2> + g|(1f7/2)
2> …. Correlated:
62.5% 24.2% 4.7% 3.8%
Even l only:
S2n=500keV
計算: by K.Hagino
|(2s1/2)2>
100%
No correlation:
(s only)
1.05b
2.41b
1.66b
SAMURAI 2012年始動予定 -- new spectrometer in RIBF --
Superconducting Analyzer for MUlti-
particle from RAdio Isotope Beam with
7Tm of bending power
RI beam from BigRIPS
target
superconducting
coil
pole(2m dia.)
rotate
vacuum chamber
Kinematically complete
measurements by detecting
multiple particles in coincidence
Superconducting Magnet
3T with 2m dia. pole (designed resolution 1/700)
80cm gap (vertical)
Heavy Ion Detectors
Proton Detectors
Neutron Detectors
Large Vacuum Chamber
Rotational Stage
Invariant Mass Measurement
Missing Mass Measurement
Proton Heavy Ion
Neutron
Slide: K. Yoneda
今後の展望
まとめ
• Dineutron 相関 --- 強い空間的相関をもつnn系
--異パリティ対相関の重ね合わせ
--弱束縛、低密度 (表面)
--(安定核の表面にも表れる可能性が指摘されている)
• クーロン分解法: 有力な手段の一つ <12>
Dalitz Plot むしろFinal Stateを調べる手段
• Coulomb Breakup of 22C
Inclusive CB Cross Section ~0.9barn (preliminary)
B(E1) ~1e2fm2 11Liと同程度
• Exclusive Coulomb Breakup of 22C 2012年度予定@SAMURAI
マクロな量の(より多数の)dineutronsがあったらどうなるか?
Neutron Skin Dineutron Skin?
ダイニュートロンの超流動状態が原子核の表面に?
2D超流動?
安定核のDineutronは本当にあるのか?
(RCNPで実験?) どういう場合にdineutron が出現するか?
Dineutron Skinはあるのか?
ボゾン的様相(超流動?)はあるのか?
弱束縛系(ハロー)のdineutron
vs 安定核のdineutron (違いは何、特徴は何)
Collaborators
Inclusive Coulomb Breakup of 22C
T.Nakamura, N.Kobayashi, Y.Kondo, Y.Satou, N.Aoi, H.Baba, S.Deguchi,
N.Fukuda, J.Gibelin, N.Inabe, M.Ishihara, D.Kameda, Y.Kawada, T.Kubo,
K.Kusaka, A.Mengoni, T.Motobayashi, T.Ohnishi, M.Ohtake, N.A.Orr, H.Otsu,
T.Otsuka, A.Saito, H.Sakurai, S.Shimoura, T.Sumikama, H.Takeda,
E.Takeshita,M.Takechi, S.Takeuchi, K.Tanaka, K.N.Tanaka, N.Tanaka,
Y.Togano, Y.Utsuno,K. Yoneda, A.Yoshida, K.Yoshida, K. Hagino
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