Motonobu Takaki(Center for Nuclear Study, Univ. of Tokyo)

Search for Double Gamow-Teller Giant Resonance

viaHeavy-Ion Double Charge Exchange Reaction

Double Gamow-Teller resonance

2νββ

στ στ

GTR

Z

Z+1

Z+2

DGTR?

~ 10-4 - 10-3 SDGT

Double Gamow-Teller resonance (DGTR) consists of two GT resonancesinduced by the spin-isospin operator, στστ.

Through the DGTR study, we would like to answer. - Is the DGTR just superposition of the GTRs,

or, do the nuclear (spin-dependent) correlations cause further changes to structure and responses of double GT states?

DGTR can be another benchmark for nuclear structure calculation of ββ-decays.- The calculation only rely on the 2νββ results.

DGTR has been left to be discovered!

A unique calibration of nuclear structure calculation for the ββ-decay.

The (ββ-decay) matrix element, however, still remains very small and accounts for only a 10−4 to 10−3 of the total DGT sum rule. A precise calculation of such hindered transition is, of course, very difficult and is inherently a subject of large percent uncertainties. At present there is no direct way to “calibrate” such complicated nuclear structure calculations involving miniature fractions of the two-body DGT transitions. By studying the stronger DGT transitions and, in particular, the giant DGT states experimentally and as we do here, theoretically, one may be able to “calibrate” the calculations of ββ-decay nuclear elements. N. Auerbach, L. Zamick, and D. Zheng, Annals of Physics 192, 77 (1989).

Limitation of experimental access to DGT

A few experiment have been attempted.

DGT: ΔL=0, ΔS=0 or 2, ΔTz=2Spin and Isospin flips is necessary.

Heavy-ion double charge exchange (HIDCX) reaction β-β- -type DGT probe is effective for medium or heavy mass nuclei

(11B, 11Li) @69MeV/A RCNP Takahisa, Ejiri et al., AIP Proc. Conf. 915, 815 (2007)

Mooderchai et. al., NPA 599, 159c (1996)Blomgren et. al., PLB 362, 34(1995)

Some strengths were found.

No clear evidence for DGTR so far… It is difficult to find a good probe

(π+,π-): spin 0 probe (18O,18Ne): β+β+ -type probe (11B,11Li): small overlap?

24Mg(18O,18Ne)24Ne @ 76 A MeV93Nb(π+,π-)93Tc

Tπ=295 MeV

New idea: (12C,12Be(0+2)) reaction

12C(gnd)→12Be(02+) transition is strong. B(GT2) ~ 0.3 　　　　　12C(18O,18Ne) experiment → Matsubara, Uesaka, MT et al., Few-Body Syst. 54, 1433 (2013).

• This is because all of the initial 12C(0+g.s.), intermediate 12B(1+g.s.) and final 12Be(0+2) state are dominated by 0ħω configuration.

Delayed-γ tagging enables clear event identification.

• τ(12Be(02+)) = 331 ns ≫ TOF ~ 150 ns (Grand Raiden)

• ~ 70% of the 12Be(0+2) state can survive and reach the focal plane.

Those two characteristics make this reaction specially effective in DGT studies.

e+e-

τ＝331 ns

Shimoura (2007)First application: 48Ca(12C,12Be(0+2)) experiment

Experimental setup

2 drift chambers FC

12C beam (100 MeV/u, 17 pnA)

Target 48Ca:10 mg/cm2

12Be

4.5 days accumulation@ RCNP, Osaka University, Japan

Identification of 12Be

12Be ~ 0.1 Hz 6He, 9Li ~ 1000 Hz t ~100000 Hz

Stopper VetoΔE1 ΔE2

ch0 200 400 600 800 1000 1200 1400 1600 1800 2000

ch

0

200

400

600

800

1000

1200

1400

1600

1800

2000E∆E vs Trigger PLS ∆ Stopper

ΔE1

Est

oppe

r

12Be9Li + 6He/t

ΔE1

Est

oppe

r

t

6He 8Li

9Li

9Li+6He/12Be?

VETO OFF VETO ON (Rejection rate = 98%)

0 200 400 600 800100012000

20

40

60

80

100

120

Identification of 12Be(0+2) with γ-ray tagging

e+e-

τ＝331 ± 12 ns

2×511 keV γ-ray in back-to-back geometry

Active stopper (plastic) + NaI scintillators

A+B exp (�t/⌧)

12Be arrival (prompt timing)

Continuous Background (11C β+, T1/2=20.4 min)

Coun

ts/20

ns

t (ns)

⌧ = 357± 49 ns

Preliminary Results: Excitation energy spectra

Prelim

inary

0 10 20 30 40 500

0.10.20.30.40.50.60 10 20 30 40 50

00.20.40.60.81

0 10 20 30 40 500

0.2

0.4

0.6

0.8

1

0 10 20 30 40 500

0.2

0.4

0.6

0.8

10 10 20 30 40 50

0

0.2

0.4

0.6

0.8

1

0 10 20 30 40 500

0.2

0.4

0.6

0.8

1

0 10 20 30 40 500

0.10.20.30.40.50.6

0 10 20 30 40 500

0.10.20.30.40.50.6

0 10 20 30 40 500

0.20.40.60.81 0.0� < ✓lab < 0.5� 0.5� < ✓lab < 1.0� 1.0� < ✓lab < 1.5�

accidental coincidence

12Be(0+2 )

12Be(0

+2 ) + Accidental coin.

Excitation Energy of 48Ti (MeV)

Nor

mal

ized

Yie

ld (A

.U.)

comparison with (π+,π-) spectrum

-5 0 5 10 15 20 25 30 350

0.1

0.2

0.3

0.4 This work48Ca(12C,12Be(0+2))48Ti0.0� < ✓lab < 0.5�

DIAS

DIAS/DGT

DGTGR?

Nor

mal

ized

Yie

ld

(A.U

.)

No apparent structure

Ex (MeV)

τ2

στ2

M. Kaletka et al., PLB 199, 336 (1987)

Summary

Double Gamow-Teller Resonances will open the research opportunity on GTR✕GTR correlation.can serve as another test bench of nuclear models relevant to ββ-decay.

Experimental access has been limited.

New idea: (12C,12Be(0+2)) reactionWe started with 48Ca(12C,12Be(0+2)) reaction @ 100 MeV/nucleon.We found strengths which not appear in 48Ca(π+,π-)48Ti reaction.The analysis to confirm the DGT strength in 48Ti is in progress.

In near future, we will achievehigher statistics with a new experiment at RIBF.to other ββ-decay nuclei (76Ge, 100Mo, 116Cd, 130Te …)

Collaborators

CNS, Tokyo S. Shimoura, M. Dozono, M. Kobayashi, K. Yako,S. Michimasa, S. Ota, M. Matsushita, S. Kawase, H. Tokieda, Y. Kubota, C.S. Lee, R. Yokoyama, H. Matsubara

RIKEN Nishina Center T. Uesaka, K. Kisamori, M. Sasano, L. Stuhl, J. Zenihiro

RCNP, Osaka A. Tamii, C. Iwamoto, Y. Matsuda, N. Aoi

Kyoto T. Kawabata, T. Furuno, M. Tsumura

Miyazaki Y. Maeda, S. Gotanda, S. Yamamoto

Comparison with Shell mode calculation

Code: Oxbash

GXPF1a interaction

2n -> 2p (in f-shell)

Calculation:K. Yako, private communication

(στ)2 spectrum in 48Ti

GND

GND

DIAS

IAS

48Ca(p,n) : Yako et al., PRL 103, 012503 (2009)

Accidental coincidence evaluation

0 200 400 600 800 1000 12000

20

40

60

80

100

120

Continuous Background (11C β+, T1/2=20.4 min)

A+B exp (�t/⌧)⌧ = 357± 49 ns

2νββ decays: One of the Double Gamow-Teller

2νββ

στ στ

GTR

Z

Z+1

Z+2

DGTR?

A unique calibration of nuclear structure calculation for the ββ-decay.

The (ββ-decay) matrix element, however, still remains very small and accounts for only a 10−4 to 10−3 of the total DGT sum rule. A precise calculation of such hindered transition is, of course, very difficult and is inherently a subject of large percent uncertainties. At present there is no direct way to “calibrate” such complicated nuclear structure calculations involving miniature fractions of the two-body DGT transitions. By studying the stronger DGT transitions and, in particular, the giant DGT states experimentally and as we do here, theoretically, one may be able to “calibrate” the calculations of ββ-decay nuclear elements. N. Auerbach, L. Zamick, and D. Zheng, Annals of Physics 192, 77 (1989).

Eliot&Vogel, (2002) ~ 10-4 - 10-3 SDGT

Single charge exchange reaction on 48Ca

48Ca(p,n) : Yako et al., PRL 103, 012503 (2009)

Go beyond and more effective

Move to RIBF- 200 - 300 MeV/u - Higher intensity- lower q

Future plan:- (12C,12Be(0+2)) w/ BigRIPS+DALI+MINOS- (10C,10Be) w/ SHARAQ

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

5

10

15

20

25

30

35

40

45

50

Be)@200 MeV/u10C,10(Be)@300 MeV/u12C,12(Be)@100 MeV/u12C,12(Li)@69 MeV/u11B,11(

More Suitable for double Gamow-Teller

excitation modes

qcm(fm-1)

Ex(

MeV

)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Be)@300 MeV/u10

C,10

(

Be)@300 MeV/u12

C,12

(

Be)@100 MeV/u12

C,12

(

Li)@69 MeV/u11

B,11

(

0j

1j

2j

d�

d⌦

����GT

/ |j0(qR)|2

qR(R=4.7 fm)j 0(qR)

DGTR

2νββ

Love & Franey

triton

F5 setup MINOS + DALI2

12C beam 1pµA

degrader

stopping 12Be and detecting delayed γ.

Low pressure MWDC 12Be

511-kev γ

(48Ca)

Statistics for each target will be 100 times larger than pervious RCNP exp.

(12C,12Be(0+2))BigRIPS+DALI+MINOS