search for double gamow-teller giant resonance via heavy ......code: oxbash gxpf1a interaction 2n...
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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
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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