Heavy-Ion Double Charge Exchange study via 12 C( 18 O, 18 Ne) 12 Be reaction Motonobu Takaki (CNS, The University of Tokyo) H. Matsubara 2, T. Uesaka 3,

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 Tokyo2National Institute of Radiological Science (NIRS)

3RIKEN Nishina Center4Research Center for Nuclear Physics, Osaka University

5Department of Physics, Kyoto University6Department 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 investigateIV 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 regionon a same footing

Intermediate energy (~ 100MeV/u)

• direct reaction process dominance

- simple reaction mechanism

• ΔL sensitivity of angular distributions

- multipole assignment

3

Co

unt

s

25 20 15 10 5 0 Ex

12C(14C,14O)12BeElab=24A MeV

W. Oertzen et al.,NPA, 588 129c (1995)

24Mg(18O,18Ne)24Ne at 76A MeV

30

20

10

0

1

0d2 σ/dΩ

c.m

.dE

(nb

/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: 18OEnergy: 80A MeVΔE: ~ 1 MeVintensity: 25 pnA

Ring Cyclotron Facility, Research Center for Nuclear Physics,

Osaka University

Grand Raiden

Energy resolution = 1.2 MeV(FWHM)

A/Q1.7 1.8 1.9 2.0 2.1 2.2

ΔE

in P

L S

cin

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-

Coupled-channel calculation with microscopic form factors

Reaction calculation

7

0+ 2+

preli

mina

ry

preli

mina

ry

one body transition density (OBTD)

form factors diff. cross section (dσ/dθ)

Shell model double folding coupled channel

NN effective int.(Love-Franey 100 MeV)

SFO int.USD int.

optical potentialglobal (double folding)

normalization factor=0.7 normalization factor=1.3

ΔL=0 ΔL=2

With appropriate normalizations, the experimental distributions were reproduced.

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

8

(p)2 dominance

Evaluation of p-shell contribution to 0+ states of 12Be

p-shell contribution in 0+g.s. and 0+

2

0+g.s.(%) 0+

2(%) 0+2/0+

g.s. methods

Meharchant 25 60 2.4±0.5 12B(7Li,7Be)

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

Similar spectroscopic value with earlier works

9

Assumption:1. 12C g.s. has only p-shell configuration. 2. The transition occurs in the 0hω

only statistical error

Double Gamow-Teller transition

B(GT2)

• This work:

- B(GT2 ) values are derived from the OBTD with the normalization factor of the cross section.

• Reference

- 12C(0+) -> 12B(1+, g.s.) (I. Daito et al., PLB 418, 27 (1998).)

- 12B(1+, g.s.) -> 12Be(0+) (R. Meharchand et al., PRL 108, 122501 (2012))

10

12Be(0+, g.s.)1st 2nd

B(GT) B(GT) B(GT2)

This work 0.17±0.04

Reference 0.999±0.005 0.184±0.008 0.184±0.009

12Be(0+2)

1st 2nd

B(GT) B(GT) B(GT2)

This work 0.27±0.07

Reference 0.999±0.005 0.214±0.051 0.214±0.05

very

preliminary

very

preliminary

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.11

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.

The microscopic calculation for the HIDCX was performed.

• The cross section can be reproduced with the appropriate normalization factors.

• B(GT)2 value is derived.

This study shows that spectroscopic studies with the HIDCX reaction are a valid and feasible!

Thank you for your attention.

Backup

13

12C(π+,π-)12O

S. Mordechai et al.,PRC, 32 999 (1985)

0 10 20 30 Ex

Co

un

ts

Co

un

ts

25 20 15 10 5 0 Ex

12C(14C,14O)12BeElab=24A MeV

W. Oertzen et al.,NPA, 588 129c (1995)

Reaction calculation scheme

14

single particle wave function one-body transition density

n-n effective interaction

double-folding transition form factor

transition density

coupled channel calculation

Calculate cross sections for various paths.

12C

12B

12Be

0+

1+

1-

0+

2+

g.s.

4.56

g.s.

7.7

Target Projectile18Ne (g.s., 0+)

18O (g.s., 0+)

18F (g.s., 1+)

GT

GT

Mixing degree between p- and sd-shell components in 0+ states of 12Be

Configuration mixing of 0+ states in 12Be

sd

1p3/2

1s1/2

1p1/2

}mixing

12Beproton neutron

(p)2 dominance

(sd)2 dominance

16

p-shell contribution in 0+g.s. and 0+

2

0+g.s.(%) 0+

2(%) 0+2/0+

g.s. methods

Meharchant 25 60 2.4±0.5 12B(7Li,7Be)

Fortune 32 68 2.1 SM

Barker 31 42 1.4 SM

Test Experiment to prove experimental feasibility

511keV

511keV

12Be

t

BG due to particlemis-identification 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

Dominance of double Gamow-Teller transition

The cross section for the 0+2 state is larger than 0+

1 (g.s.).

Double GT transitions dominate in two 0+ states.

→ Sensitive to the 0 ωℏ configuration

Our experimental result

Single charge exchange reaction result