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

90Zr, 208Pb(t,3He) at 300 MeV/u (Miki et al.)

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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

90Zr(12N,12C) at 200 MeV/u (Noji et al.)

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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.

7Li, 90Zr (10C,10Bg) at 200 MeV/u (Sasamoto et al.)

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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.)