Heavy-Ion Double Charge Exchange study via 12C(18O,18Ne)12Be

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!
1
!
CNS, The University of Tokyo!
2
National Institute of Radiological Science (NIRS)!
3
RIKEN Nishina Center!
4
Research Center for Nuclear Physics, Osaka University!
5
Department of Physics, Kyoto University!
6
Department 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…
12C(π-,π+)12Be
J.E. Ungar et al., PLB, 144 333 (1984)
S. Mordechai et al., PRL 60, 408 (1988).
2
HIDCX with Missing mass method !
at Intermediate energy
Heavy-ion!
12C(14C,14O)12Be!
• Double Spin and/or Isospin flip (ΔS=2, ΔTz=2)!
Counts
Missing mass method!
Sn
Elab=24A MeV
• measure All excitation energy region on a same footing!
25
Intermediate energy (~ 100MeV/u)!
• ΔL sensitivity of angular distributions!
- multipole assignment
We performed 12C(18O,18Ne) reaction experiment!
in normal kinematics at 80 MeV/nucleon.
(nb/sr/(0.5 MeV))
- simple reaction mechanism!
15
10
5
0 Ex
W. ! Oertzen et al.,"
NPA, 588 129c (1995)
d2σ/dΩc.m.dE
• direct reaction process dominance!
20
30
24Mg(18O,18Ne)24Ne
!
at 76A MeV
20
10
0
1
J. Blomgren et al.!
PLB, 362 34 (1995)
0
0
24Ne
5 10 15 20
excitation energy (MeV)
3
(18O,18Ne) reaction
Ground states of 18O and 18Ne are among the same super-multiplet.!
• simple transition process!
• large transition probability!
!
B(GT) ~ 0.07
!
!
!
B(GT)=0.11
τ
τ
18O
στ
B(GT)=3.15
18F
στ
B(GT)=1.05
B(GT) ~ 0
18Ne
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
Setup of the experiment
Good PID resolution
Energy resolution = 1.2 MeV(FWHM)
18
18Ne
1400
F
17
F
ΔE in PL Scint.
17
O
E (arb. unit)
1200
1000
Grand Raiden
18Ne
15
O
14
O
15
N
14
N
13
N
13
800
12C
O
16
C
12
C
11
target (2.2 mg/cm2)
12
N
600
1.7
C
11
1.8
1.9
2
2.1
B
2.2
A/Q
1.7 1.8 1.9 2.0
2.1 2.2
18O
MWDCs and plastic scinti.
beam
beam: 18O
Energy: 80A MeV
ΔE: ~ 1 MeV
intensity: 25 pnA
A/Q
2.3
18Ne
Ring Cyclotron Facility, !
Research Center for Nuclear Physics, !
Osaka University
5
Successful result
!
!
!
2+/3-
!
!
!
!
!
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
Probing of the configuration mixing
Mixing degree between p- and sd-shell components in 0+ states of 12Be!
!
sd
!
} mixing
1p1/2
!
1p3/2
!
(p)2 dominance
!
!
1s1/2
proton
12Be
neutron
!
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.
7
Evaluation of p-shell contribution to 0+ states of 12Be
Assumption:!
1. 12C g.s. has only p-shell configuration. !
2. The transition occurs in the 0hω
relative cross section between 0+g.s. and 0+2!
←→ ratio of p-shell contributions
+
(02 )/
+
(0g.s. )
= 2.4(2)
only statistical error
Similar spectroscopic value with earlier works
p-shell contribution in 0
0+
0+
0
methods
12
Meharchant
25
60
2.4±0.5
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)
8
Conclusion
!
!
!
2+/3-
!
!
!
!
!
!
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
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 suggest a sensitivity to multipolarities.!
!
This study shows that spectroscopic studies with the HIDCX reaction are a valid and feasible!
Thank you for your attention.
Counts
Backup
12C(14C,14O)12Be!
12C(π+,π-)12O
Counts
Elab=24A MeV
0
10
Ex
S. Mordechai et al.,!
PRC, 32 999 (1985)
20
30
25
20
15
10
5
0 Ex
W. !Oertzen et al.,!
NPA, 588 129c (1995)
11
Test Experiment to prove experimental feasibility
18O(12C,12Beγ)18Ne(gnd)
Counts (A.U.)
Excitation Energy
Counts (A.U.)
Decay Time
2γ time spectrum
12
decay time
Fit
10
decay time constant: 395(+173-92) ns
decay time constant:
395+173
-92 ns
⇔ 331 ns in literature
8
18
180
160
18
18
O(12C,12Be) Ne w/o -ray tag
w/o γ-tag
6
4
18
O(12C,12Be(0+)) Ne w/ -ray tag × 10
2
18
Ne(gnd)
140
y
r
a
n
i
120
100
80
60
2
0
0
m
i
l
BG
due to particle
e
r
pmis-identification
200
400
600
800
511keV
with γ-tag
×10
t
40
12Be
20
0
-20
511keV
-15
-10
-5
0
5
10
15
20
Ex (A.U.)
1000 1200 1400
Time
(ns)
Time
[ns]

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