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

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