The ICHOR project : spinisospin response study for 22 decay and magnetic spectrometer SHARAQ

1
The ICHOR project spin-isospin response study
(for 2?2ß decay) and magnetic spectrometer
SHARAQ
The third LACM-EFES-JUSTIPEN Workshop at Oak
Ridge
February 23-25, 2009

• H. Sakai
• University of Tokyo

2
What is the ICHOR project ?
Isospin-spin responses in CHarge-exchange
exOthermic Reactions ( Grant-in-Aid of MEXT )

• 1. Study of the intermediate nuclear structure
  for 2?2ß decay
• ?48Ca(p,n)48Sc and 48Ti(n,p)48Sc reactions at
  300 MeV
• 2. The magnetic spectrometer SHARAQ construction
  at RIBF in RIKEN
• ? present status

• Based on the works by
• K. Yako (for 2?2ß decay)
• SHARAQ collaboration

3
Study of intermediate nuclear structure of 48Sc
for 48Ca 2?2ß decay via. (p,n) and (n,p)
reactions at 300 MeV
Courtesy by K. Yako
4
Two-neutrino double beta decay
2?ßß decay
(A,Z1)
daughter
(A,Z)

• second order weak process.
• rarest process confirmed so far.
• 2?ßß is very useful to test theoretical models.
• Same models are used for 0?ßß analysis.

parent

intermediate
(A,Z2)
Half lives not understood well
Suhonen et al., PR300(1998)123
Half-life and matrix element
T1/2 is not enough to test theories.
5
B(GT) in low-lying states of 48Sc
GT strengths ? charge exchange reactions at
intermediate energies
(p,n) type
Grewe et al., PRC76(2007)054307
(3He,t)
(n,p) type
48Sc
(d,2He)
48Ca
4276 keV
48Ti
Low lying states high resolution measurements
48Ca(3He,t) _at_ 140A MeV (RCNP) 48Ti(d,2He) _at_ 90A
MeV (KVI)
6
Contribution of low-lying states
Grewe et al., PRC76(2007)054307
matrix element w/o sign
No sign info, always additive sum ? upper
limit
Decay measurement
NEMO3 (preliminary)
(4.4 0.4) x 1019 y
0.5 - 0.4
M2v? 0.045 MeV-1
Are these B(GT) distributions good enough to test
nuclear structure models? , Of course NOT.
7
Shell model calculation
Same as Horoi et al. PRC75(2007)034303
Reproduce low energy part rather well!
Shell model (full fp)

• GXPF1A
• QF 0.6

GT GR
Only 5 of total B(GT-)!
w/o sign
8
Aim

• Measure full profile of the B(GT) distribution to
  test /constrain theoretical models.
• Measurement
• B(GT/-) distributions
• Ebeam 300 MeV
• ? 012

GTGR
?
48Ca(p,n)48Sc 48Ti(n,p)48Sc
116Cd(p,n)116In 116Sn(n,p)116In
(p,n)
(n,p)
48Sc
48Ca
48Ti
9
(p,n) (n,p) facilities at RCNP
100 m TOF tunnel

• 2x106 neutrons/s
• by 7Li(p,n)

LAS
10
Measurement and results on 48Ca(p,n)48Sc and
48Ti(n,p)48Sc reactions at 300 MeV
11
48Ca(p,n) measurement

• 48Ca target
• 17 mg/cm2, 98
• energy resolution
• 410 keV
• angular range
• 0 41 deg

12
48Ti(n,p) spectra

• angular range
• 0 -12 deg
• energy resolution
• 1.2 MeV
• statistical accuracy
• 1--3 / 2MeV1deg
• systematic uncertainty
• 4

3 x 300 mg/cm2, 2 x 3 cm2 (c.f. Alford et al.
130mg/cm2)
13
Multipole decomposition analysis
48Ti(n,p) angular dist. Ex 15 MeV
MDA
DWIA
DWIA inputs

• NN interaction
• t-matrix by Franey Love _at_325 MeV
• optical model parameters
• Global optical potential
• (phenomenological, Cooper et al.)
• one-body transition density
• pure 1p-1h configurations
• radial wave functions W.S. / H.O.

Particle 1f, 2p, 1g, 2d, 3s, 1h11/2 Hole 1p,
1d, 2s, 1f
14
Reliability of angular distribution
The DWIA description of GT transition is good.
The description of ?L2 is reasonable.
The ?Lgt4 component does not contribute much at 0
Using only ?L0,1,2,3 seem to be justified.
15
Sasano/Miki
Decomposed spectra
16
Proportionality relation
Deducing B(GT) using proportionality relation
Sasano
kinematical correction by DWIA
GT unit cross section
A-dependence of (p,n) _at_ 300 MeV
Same used for both (p,n) and (n,p).
17
B(GT/-) distribution
MD analysis (p,n) strength exists
beyond GTGR (n,p) peak at 3 MeV
shoulder at 6 MeV bump(?) at 12 MeV
Integrated strengths
(Ex lt 30 MeV)
New
SB(GT-) 15.32.2 SB(GT) 2.80.3
Ex lt 5 MeV consistent with
(3He,t ) (d,2He)
Contamination of IVSM?
isovector spin monopole ?S1, ? L 0,
2h?, Op r2st
contribution estimated by DWIA 1.0 for (p,n),
0.9 for (n,p)
18
B(GT/-) distribution comparison with shell
model
Shell model with quenched
operator Spectra are well reproduced up to
(p,n) Ex 15 MeV (n,p) 8
MeV Strengths beyond underestimated.
QF 0.6
(n,p) channel SB(GTexp) 1.90.3 (w
subtraction of IVSM) SB(GTShellModel) 0.9

larger model space? deformation?
19
Contribution to M2v
At 8 MeV lt Ex lt 15 MeV dB(GT-)/dE large ?
excess B(GT) might have significant
contribution on M2v.
matrix elements w/o sign
Consequence of (true) matrix element with sign
unknown. We must rely on theorists.
20
QRPA prediction by Rodin (preliminary)
QRPA G-matrix gpp No quenching (QF
1.0)
21
Summary for 2?2ß decay

• The cross section spectra were measured at 300
  MeV for
• the 48Ca(p,n)48Sc / 48Ti(n,p)48Sc reaction
• MD analysis ? B(GT/-) distribution (Ex lt 30
  MeV)
• 48Ca ? 48Sc ? 48Ti
• SB(GT-) 15.32.2 SB(GT) 2.80.3
• shell model predictions
• B(GT-) good agreement up to GTGR.
• B(GT) reasonable for Ex lt 8 MeV,
  underestimate for Ex gt 8 MeV.
• QRPA by Rodin
• B(GT) IVSM is important?
• M2? large contribution from excited GT states.
• Uncertainty remains due to the IVSM contribution.
• ? to be explored by SHARAQ magnetic
  spectrometer
• under the ICHOR project.

22
The magnetic spectrometer SHARAQ at RIBF in RIKEN
(under the ICHOR Project)

• what is new? unstable nucleus as a probe

23
Spin-isospin responses and reaction kinematics

• Reaction kinematics dictates q and ? relation.

? Stable nuclear beam excites only ? lt q reagion
(space-like)!

• Interesting Spin-isospin responses often
• locate at qsmall at high ?. For example

• Double Gamow-Teller (DGT) resonance
• Isovector Spin Monopole (IVSM) resonance

• ?gt0 and q 0 (time-like) can be reached by
• exothermic HICE reactions.

24
New idea to use unstable nuclei
Courtesy of Shimoura

• With stable beam
• With unstable beam

Dm gtgt 0 EXOTHERMIC
Photon Line
Dm / g
Dm lt 0 endothermic
Tz
RI beam is capable to probe the w gt q region.
25
Example of exothermic CE reactions

• Exothermic CE reactions (12B,12C)/(12N,12C)
• Q13 MeV/ 17 MeV
• Endothermic CE reactions (12C,12N)/(12C,12B)
• Q-17 MeV/ -13 MeV

exothermic CE reaction achieves qsmall with an
excellent spin-isospin selection,?S1, ?T1
Energy resolution for spectroscopy DE 500keV
for A12?E/A300MeV particle 0.5MeV/(30012)MeV
1.310-4 ? corresponds to momentum resolution
of p/Dp 15000 Angular resolution ? momentum
transfer resolution ex. 12N, 300MeV/A 9GeV/c C
RITERION Dq lt 0.1 fm-1 Dq p(beam)Dq ?
Dq lt 2 mrad Dq 1 mrad
Intense unstable beams
Dispersion matching BL
Magnetic spectrometer
26
Lets look at the magnetic spectrometer SHARAQ
27
What is SHARAQ?

• SHARAQ is a high resolution magnetic spectrometer
• for unstable (secondary) beam experiments.
• Installed at RIBF of RIKEN

Expected intensity (14N 250 MeV/A) 12N
1.6105 cps/pnA (max. 4107 cps) 12B 2.8105
cps/pnA (max. 7107 cps)
d,.,238U 350MeV/nucl. ? RI beam
by fragmentation
28
SHARAQ Characteristic

• QQDQD type
• Maximum rigidity 6.8 Tm
• Dp/p 14700
• Dispersion matching (xd), (qd)
• Angular resolution lt 1 mrad
• Solid angle 2.7 msr / 4.8 msr
• Rotatable (-2 to 15 degree)
• Weight 500 tons

A/Z3 220MeV/A
29
Documentary film of SHARAQ construction

• Experimental room E20 _at_RIBF
• 14 July 2007 19 October 2007

30
Present SHARAQ
Commissioning run starts March 23, 2009 !
First accepted experiment search for IVSMR(b )
by (t,3He) reaction
31
IVSMR(b ) search by SHARAQ
Courtesy by K. Miki

• IVSM operator

DL0, DS1, DT1, 2?w

• Compression mode

experimental data IVSMR(b -) some
signatures observed IVSMR(b ) none
32
Thank you for your attention.
33
Backup
34
116Cd(p,n) 116Sn(n,p) results
Sasano
B(GT) distributions
The ?L0 strengths seem to be underestimated (if
QF0.6).
35
48Ca(p,n) Other multipoles
MDA by sasano
Spectra
Double differential cross section (a.u.)
Excitation energy (MeV)
Reliability
reliability
good
poor

• ?L0 component is the most stable.
• ?Lgt0 components suffer from node ambiguity.
  (02h?, 13h?)
• Uncertainty due to the unbound final states.

One must be careful extracting ?Lgt0 components in
high Ex region.
36
Concerns

• IVSM
• should be confirmed by surface probes
• measurement with heavy ion beams.
• Interference with GT?
• Uncertainty due to reaction mechanism in the
  continuum
• Transition density
• Quasifree scattering around 0 degrees

37
(p,n) (n,p) at 300 MeV
Advantages

• 300 MeV
• Distortion effects are smallest ( ).
• ? Analysis with DWIA is reliable.
• SF/NSF is largest ( ).
• ? Transitions are mostly SF type.
• Tensor interaction is smallest ( ).
• ? Proportionality relation is reliable.

strength
cross section
Most reliable multipole decomposition analysis
(MDA) is possible.
tensor FraneyLove
38
Proportionality test by shell model
Sasano
48Ca(p,n)48Sc
48Ti(n,p)48Sc

• Exercise by using
• 48Ca--48Ti system
• Shell model calc. (n 4)
• Standard DWIA calc.

unit cross section (A.U.)
Deviations are small for large B(GT) for both
sides.
1
0.01
B(GT-)
B(GT)
39
116Cd(p,n) at 140 MeV vs. 116Cd(3He,t)
Akimune et al. (1997)
0spectrum

• GT component 0 MeV
• Poor agreement with
• (3He,t) spectrum

counts
E293 (Sasano)
40
Controversy with (3He,t) result(group)
41
Contribution of g.s. in 116In to M2?
intermediate
1
Contribution of g.s.
g.s.
1

• B(GT-) 0.26 0.02 (This work)
• B(GT) 0.256 0.001 (ß decay)

116In
0
116Cd
0
?
M2?(g.s.) 0.070 0.003 (MeV-1)
116Sn
2?ßß decay measurement
?
M2?(total) 0.064 0.007 (MeV-1)
Transition through g.s. accounts for the
half-life of 116Cd.
running sum of M2?(76Ge)
Single-state dominance is not
necessarily universal.
imkovic et al., NPA733(2004)321
42
Nuclear matrix elememnt of 0?ßß decay
J. Suhonen, 2005
lt 1995
1995 - 2000
gt 2000
43
Values from the Majorana Collaboration web site
(2006)
43
Courtesy of J.P. Schiffer
44
(n,p) measurement
(n,p) ????
(n,p) facility

• 2x106 neutrons/s
• by 7Li(p,n)
• angular range of
• 0-12deg is covered
• by 3 angular setting
• of LAS

45
48Ti target
Alford et al., NPA514(1990)49

• 48Ti(n,p) at TRIUMF (1990, Alford et al.)
• metal 48Ti thin low statistics
• Data at 3 angles
• not enough for MD analysis
• 48TiO2 contribution of oxygen
• at Ex gt 6 MeV

• metallothermic reduction
• (IIS, Okabe Gr.)
• TiO2 2Ca Ti 2CaO
• 48TiO2 13g ? 48Ti 5g (70)
• purity 98.7
• 2. solidification by pressure
• 3 x 300 mg/cm2, 2 x 3 cm2
• (c.f. Alford et al. 130mg/cm2)

46
Decomposed angular distributions 48Ti(n,p)
by Miki
1.0 MeV
9.0
17.0
Double differential cross section (mb / sr / MeV)
11.0
19.0
3.0 MeV
0 5 10
0 5 10
0 5 10
Scattering angle (deg)
?L0
?L1
?L2
?L3
47
??????
Courtesy of K. Muto
48Ca ? 48Ti
???,??????????? Gamow-Teller ??????????,??????????
?????
Gamow-Teller ????????
48Ti ? 48Sc ? Gamow-Teller ???????????
???
???
????
???????????????????? Gamow-Teller ????(????)?????
48
B(GT-) ? B(GT) ?????
Courtesy of K. Muto
????
49
Some concern by Amos, Faessler and Rodin
Proportionality
questioned.

• Exercised by using
• 76Ge--76Se system
• QRPA calculation
• DWA

50
Proportionality test by QRPA
Transition density QRPA
Amos, Faesler Rodin, PRC76(2007)014614
Reaction code
Sasanos calc.
DW81
Confirmed
The proportionality in the (n,p) channel looks
worse.
(n,p)
(p,n)
but not so serious !
51
Proportionality test by Shell model
Sasano
48Ca(p,n)48Sc
48Ti(n,p)48Sc

• Exercise by using
• 48Ca--48Ti system
• Shell model calculations
• Standard DWIA calc.

unit cross section (A.U.)
1
0.01
Deviations are large for small B(GT) for both
sides.
B(GT-)
B(GT)
Average ( ) works very well!
52
Proportionality test-2 by Sasano
What is the reason of spread?
full int.

• Exercise by using
• 58Ni system
• Shell model calculations
• Standard DWIA calc.
• with/without tensor interactions

Deviations are mainly due to the tensor
interactions.
wo tensor int.
53
Results on 116Cd(p,n)116In, 116Sn(n,p)116In
reactions
54
116Cd(p,n) 116Sn(n,p) results
Sasano
B(GT) distributions
BB
IVSM?
GT
dB(GT)/dEx (MeV-1)
GT-