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Heavy-Ion Double Charge Exchange study !via 12C(18O,18Ne)12Be reaction
Motonobu Takaki!(CNS, The University of Tokyo)!
!H. Matsubara2, T. Uesaka3, N. Aoi4, M. Dozono1, T. Hashimoto4, T. Kawabata5,
S. Kawase1, K. Kisamori1, Y. Kubota1, C.S. Lee1, J. Lee3, Y. Maeda6, S. Michimasa1,K. Miki4, S. Ota1, M. Sasano3, T. Suzuki4, K. Takahisa4, T.L. Tang1, A. Tamii4,
H. Tokieda1, K. Yako1, R. Yokoyama1, J. Zenihiro3, and S. Shimoura1!
!1CNS, The University of Tokyo!
2National Institute of Radiological Science (NIRS)!3RIKEN Nishina Center!
4Research Center for Nuclear Physics, Osaka University!5Department of Physics, Kyoto University!
6Department of Applied Physics, University of Miyazaki
2nd conference on ARIS 2014, June 2nd 2014
Double Charge eXchange (DCX) reaction
Probe for unstable nuclei!• Using stable target with ΔTz = 2!
Powerful tool to investigate IV Double Giant Resonances!• DIAS, DIVDR…
2
12C(π-,π+)12Be
J.E. Ungar et al., PLB, 144 333 (1984)S. Mordechai et al., PRL 60, 408 (1988).
HIDCX with Missing mass method !at Intermediate energy
Heavy-ion!• Double Spin and/or Isospin flip (ΔS=2, ΔTz=2)!
Missing mass method!• measure All excitation energy region
on a same footing!
Intermediate energy (~ 100MeV/u)!• direct reaction process dominance!
- simple reaction mechanism!
• ΔL sensitivity of angular distributions!
- multipole assignment
3
Cou
nts
25 20 15 10 5 0 Ex
12C(14C,14O)12Be!Elab=24A MeV
W. ! Oertzen et al.,"NPA, 588 129c (1995)
24Mg(18O,18Ne)24Ne !at 76A MeV
30
20100
1
0d2σ/
dΩc.
m.d
E (n
b/sr
/(0.5
MeV
))0 5 10 15 20
24Ne excitation energy (MeV)
J. Blomgren et al.!PLB, 362 34 (1995) We performed 12C(18O,18Ne) reaction experiment!
in normal kinematics at 80 MeV/nucleon.
Sn
(18O,18Ne) reaction
Ground states of 18O and 18Ne are among the same super-multiplet.!• simple transition process!
• large transition probability!
!
!
!
!
A primary 18O beam is employed!• high intensity (> 10 pnA)!
Experiment can be performed at RCNP with GR spectrometer !• high quality data with high energy resolution
4
τ τ
στστB(GT)=3.15 B(GT)=1.05
18O18F
18Ne
B(GT)=0.11
B(GT) ~ 0.07
B(GT) ~ 0
Setup of the experiment
5
12C target (2.2 mg/cm2)
MWDCs and plastic scinti.
18O beambeam: 18O Energy: 80A MeV ΔE: ~ 1 MeV intensity: 25 pnA
Ring Cyclotron Facility, !Research Center for Nuclear Physics, !
Osaka University
Grand Raiden
Energy resolution = 1.2 MeV(FWHM)
600
800
1000
1200
1400
1.7 1.8 1.9 2 2.1 2.2 2.3A/Q
�E (a
rb. u
nit)
18Ne
14O
12N11C
13N
15O
17F
16O
14N
12C
15N
13C
11B
18F
17O
A/Q1.7 1.8 1.9 2.0 2.1 2.2
ΔE in
PL
Scin
t.
18Ne
18Ne
Good PID resolution
Successful result
!
!
!
!
!
!
!
!
Bound and unbound states were observed in one-shot measurement.!
The 2.2 MeV peak has a larger cross section than the g.s.!
Different angular distribution of the 4.5 MeV peak.6
2+/3-
Probing of the configuration mixing
Mixing degree between p- and sd-shell components in 0+ states of 12Be!
!
!
!
!
!
!
!
The cross section for the two 0+ states at forward angle!➡dominated by double Gamow-Teller transition(ΔL=0, ΔS=2, ΔT=2).!
➡mainly reflect the p-shell contribution.
sd
1p3/2
1s1/2
1p1/2
}mixing
12Beproton neutron
7
(p)2 dominance
Evaluation of p-shell contribution to 0+ states of 12Be
p-shell contribution in 0
0+ 0 0+ methods
Meharchant 25 60 2.4±0.5 12
Fortune 32 68 2.1 SM
Barker 31 42 1.4 SM
R. Meharchant et al., PRL 122501, 108 (2012) H. T. Fortune et al., PRC, 024301, 74 (2006) F. C. Barker, Journal of Physics G, 2(4), L45 (1976)
relative cross section between 0+g.s. and 0+2!←→ ratio of p-shell contributions
�(0+2 )/�(0+g.s.) = 2.4(2)
Similar spectroscopic value with earlier works
8
Assumption:!1. 12C g.s. has only p-shell configuration. !2. The transition occurs in the 0hω
only statistical error
Conclusion
!
!
!
!
!
!
!
!
!
The 2.2 MeV peak has a larger cross section than the g.s.!• The p1/2 component dominantly contributes to the 0+2 state.!
The different angular distribution of the 4.5 MeV peak!• The HIDCX reaction can assign multipolarities.
9
2+/3-
Summary
HIDCX reactions are unique probe for light unstable nuclei and IV double giant resonances, especially spin-flip excitations. !
The HIDCX 12C(18O,18Ne) reaction experiment was performed.!• Three clear peaks were observed at Ex=0.0, 2.2 and 4.5 MeV.!
• Larger cross section for the 12Be(0+2) state reflects the degree of the p-shell contribution for the two 0+ states in 12Be.!
• The different angular distributions of the cross sections suggesta sensitivity to multipolarities.!
!
This study shows that spectroscopic studies with the HIDCX reaction are a valid and feasible!
Thank you for your attention.
Backup
11
12C(π+,π-)12O
S. Mordechai et al.,!PRC, 32 999 (1985)
0 10 20 30 Ex
Cou
nts
Cou
nts
25 20 15 10 5 0 Ex
12C(14C,14O)12Be!Elab=24A MeV
W. !Oertzen et al.,!NPA, 588 129c (1995)
Ex (A.U.)-20 -15 -10 -5 0 5 10 15 20
Cou
nts (
A.U
.)
0
20
40
60
80
100
120
140
160
180
Excitation Energy
preliminary
Ne(gnd)18
-ray tagaNe w/o 18Be)12C,12O(18
10×-ray tag aNe w/ 18))2+Be(012C,12O(18
Test Experiment to prove experimental feasibility
511keV
511keV
12Be
t
BG due to particle mis-identification
Time (ns)0 200 400 600 800 1000 1200 1400
Cou
nts (
A.U
.)
0
2
4
6
8
10
12
Decay Time
decay time
Fit
decay time constant: 395(+173-92) ns
decay time
Fit
decay time constant: 395(+173-92) ns
decay time
Fit
decay time constant: 395(+173-92) ns
with γ-tag ×10
w/o γ-tag
18O(12C,12Beγ)18Ne(gnd)2γ time spectrum
Time [ns]
decay time constant: 395+173 ns ⇔ 331 ns in literature
-92
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