spin-isospin studies with the sharaq spectrometer tomohiro uesaka & y. sasamoto, k. miki, s....
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Spin-isospin studies with the SHARAQ Spectrometer
Tomohiro Uesaka &
Y. Sasamoto, K. Miki, S. NojiUniversity of Tokyo
for the SHARAQ collaboration
Aizu2010
Nov 10-13, 2010
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RI beam factory @ RIKEN
Superconducting
Ring Cyclotron (SRC)
Isotope separator
BigRIPSSHARAQ
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What is SHARAQ?
SHARAQ is a HIGH-RESOLUTION magnetic spectrometer
constructed at RIBF by University of Tokyo - RIKEN collaboration.
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SDQ
D1
D2
Q3
Design Specifications of SHARAQ
Maximum rigidity
6.8 Tm
Momentum resolution
dp/p = 1/14700
Angular resolution
~ 1 mrad
Momentum acceptance
± 1%
Angular acceptance
~ 5 msr
QQDQD
T.U. et al., NIMB B 266 (2008) 4218.
"GANIL-made"
CRDC
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Nuclear Spin-Isospin Responses
For more than 70 years, we have dedicated our efforts to study of nuclear spin-isospin responses.
→ knowledge of fundamental properties of finite nuclei and infinite nuclear matter
in-medium interactioncorrelation in nuclei
→ essential inputs to
astrophysics nucleo-synthesis, neutron star physics . . . neutrino physics weak response of nuclei
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Isovector monopole resonances
Isovector monopole resonances
higher tone of GT & IAS
DT=1
DL=0
DS= 0, 1
2hw excitations
Experimental data are scarce.
no good (efficient) probes to probe IV(S)MR so far
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RI beams induced charge exchange reactions
Spectroscopy with RI-beam induced reactionsTraditional example: (t,3He) experiments
POTENTIAL of (new) RI beam induced reactions
New SELECTIVITIES (DT, DS, DL, Dp) missing in stable-beam induced reactions
ex. the (10C,10B*(IAS)) reaction to probe isovector non-spin-flip (DT=1, DS=0) excitations.
→ search for Isovector Monopole Resonances
Access to kinematical region which are inaccessible by stable beams. large Q-value in RI beam induced charge exchange reaction (exothermic)
→ RECOILLESS excitation of HIGH-Ex states Isovector Spin Monopole Resonance via the (12N,12C) reaction Double Gamow-Teller Resonance via the (10C,10Be) reactions Tetra-neutron state via the 4He(8He,8Be[=2a]) reaction
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First series of experiments with SHARAQ
Studies of IV(S)MR, taking advantages of
RI beam induced charge exchange reactions (RICE)
• 90Zr, 208Pb(t,3He) at 300 MeV/u (Miki et al.)
search for b+ type isovector spin monopole resonances
• 7Li, 90Zr (10C,10Bg) at 200 MeV/u (Sasamoto et al.)
search for b+ type isovector non-spin monopole resonances
• 90Zr(12N,12C) at 200 MeV/u (Noji et al.)
establish exothermic charge exchange reaction to probe
b- type isovector spin monopole resonances
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Experimental conditions
Beam Primary : 4He 320MeV/u 300pnA Secondary : triton 300MeV/u 1x107pps Purity > 99%Obtained spectra 208Pb(t ,3He) 208Tl 90Zr (t ,3He) 90Y
Resolution(FWHM) DE ~ 2.5MeV - energy spread of 2nd beam – 1.9MeV - energy loss in target – 1.4MeV Dq ~ 0.5deg - angular spread of 2nd beam – 7mrad - multiple scattering in target – 6mrad
0 < Ex < 70 MeV
0 < q < 3 deg@
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• Stat. accuracy (0deg) ~ 2% for 1msr ・ 1MeV –bin
• Bumps at 4MeV, 15MeV -- peak around the forward angle
DL=0 ?
208Pb(t,3He)208Tl @ 300MeV/u
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IVSMR( b +) for 208Pb
• IVSMR(DL=0) Forward-peak• Comparison between
0.0-0.5 deg .vs. 0.5-1.0 deg spectra
Miki et al.
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IVSMR( b +) for 208Pb
• IVSMR(DL=0) Forward-peak• Comparison between
0.0-0.5 deg .vs. 0.5-1.0 deg spectra• Significant DL=0 component
around 12MeV
First observation of
b+-type IVSMR
Miki et al.
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• IVSMR(DL=0) Forward-peak• Comparison between
0.0-0.5 deg .vs. 0.5-1.0 deg spectra• Significant DL=0 component
around 12MeV
• Theoretical predictions : TDA(SGII) , TDA(SIII) Hamamoto, Sagawa : Phys.Rev.C 62 (2000) 024319
IVSMR( b +) for 208Pb
IVSMR
TDA(SIII) reproduces the data well.
First observation of
b+-type IVSMR
Miki et al.
Very Preliminary
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• IVSMR(DL=0) Forward-peak• Comparison between
0.0-0.5 deg .vs. 0.5-1.0 deg spectra• Significant DL=0 component
around 20MeV
• Theoretical predictions : TDA(SGII) , TDA(SIII) Hamamoto, Sagawa : Phys.Rev.C 62 (2000) 024319
IVSMR( b +) for 90Zr
SDR
IVSMR
Detailed analyses to deduce absolute value
of the transition strength are in progress
Miki et al.
Very Preliminary
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b- type IVSMR
(12N,12C) reaction at 200 - 300 MeV:
BEST probe to b- type IVSMR
Selective excitation of st mode12N(1+) → 12C (0+)
Surface sensitivity (HI reaction)
Exothermic reaction
good momentum matching
90Zr(12C, 12N) data were taken
Analysis to subtract BG is now
being done.
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(10C,10Bg) Reaction
• Use super-allowed Fermi transition (in projectile)
to probe isovector non-spinflip mode in target nuclei
DT=1, DS=0
NO stable beam induced
reaction with the selectivity
• 1022 keV g-ray is a signature of
the non-spinflip transition
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7Li(10C,10Bg) : proof of the principle
1022 keV g-ray
Sasamoto et al.
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Search for IV-nonspin-MR in 90Zr
Sasamoto et al.
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Summary
• RI beam induced charge exchange (RICE) reactions can be tools
to probe hardly studied states such as
IV(S)MR
double GT states. . .
• In the first series of SHARAQ experiments, IV(S)MR are
studied by taking advantage of RICE
90Zr, 208Pb(t,3He) at 300 MeV/u (Miki et al.)7Li, 90Zr (10C,10Bg) at 200 MeV/u (Sasamoto et al.)90Zr(12N,12C) at 200 MeV/u (Noji et al.)