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Spin- isospin studies with the SHARAQ Spectrometer

Aizu2010 Nov 10 - 13, 2010. Spin- isospin studies with the SHARAQ Spectrometer. Tomohiro Uesaka & Y. Sasamoto , K. Miki, S. Noji University of Tokyo for the SHARAQ collaboration. RI beam factory @ RIKEN. Superconducting Ring Cyclotron (SRC). Isotope separator BigRIPS. SHARAQ.

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Spin- isospin studies with the SHARAQ Spectrometer

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  1. Aizu2010 Nov 10-13, 2010 Spin-isospin studies with the SHARAQ Spectrometer Tomohiro Uesaka & Y. Sasamoto, K. Miki, S. Noji University of Tokyo for the SHARAQ collaboration

  2. RI beam factory @ RIKEN Superconducting Ring Cyclotron (SRC) Isotope separator BigRIPS SHARAQ

  3. What is SHARAQ? SHARAQ is a HIGH-RESOLUTION magnetic spectrometer constructed at RIBF by University of Tokyo - RIKEN collaboration.

  4. Design Specifications of SHARAQ T.U. et al., NIMB B 266 (2008) 4218. Maximum rigidity 6.8 Tm Momentum resolution dp/p = 1/14700 Angular resolution ~ 1 mrad Momentum acceptance ± 1% Angular acceptance ~ 5 msr SDQ QQDQD D1 Q3 D2 "GANIL-made" CRDC

  5. 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 interaction correlation in nuclei → essential inputs to astrophysics nucleo-synthesis, neutron star physics . . . neutrino physics weak response of nuclei

  6. 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

  7. RI beams induced charge exchange reactions Spectroscopy with RI-beam induced reactions Traditional 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-Exstates 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

  8. 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 isovectornon-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

  9. 90Zr, 208Pb(t,3He) at 300 MeV/u (Miki et al.)

  10. 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 @

  11. 208Pb(t,3He)208Tl @ 300MeV/u • Stat. accuracy (0deg) ~ 2% for 1msr ・1MeV –bin • Bumps at 4MeV, 15MeV -- peak around the forward angle DL=0 ?

  12. IVSMR(b +) for 208Pb Miki et al. • IVSMR(DL=0)  Forward-peak • Comparison between0.0-0.5 deg .vs. 0.5-1.0 deg spectra

  13. IVSMR(b +) for 208Pb Miki et al. • IVSMR(DL=0)  Forward-peak • Comparison between0.0-0.5 deg .vs. 0.5-1.0 deg spectra • Significant DL=0 component around 12MeV First observation of b+-type IVSMR

  14. IVSMR(b +) for 208Pb Miki et al. • IVSMR(DL=0)  Forward-peak • Comparison between0.0-0.5 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 Very Preliminary First observation of b+-type IVSMR IVSMR TDA(SIII)reproduces the data well.

  15. IVSMR(b +) for 90Zr Miki et al. • IVSMR(DL=0)  Forward-peak • Comparison between0.0-0.5 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 Very Preliminary IVSMR SDR Detailed analyses to deduce absolute value of the transition strength are in progress

  16. 90Zr(12N,12C) at 200 MeV/u (Noji et al.)

  17. b- type IVSMR (12N,12C) reaction at 200－300 MeV: BEST probe to b- type IVSMR Selective excitation of st mode 12N(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.

  18. 7Li, 90Zr (10C,10Bg) at 200 MeV/u (Sasamoto et al.)

  19. (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

  20. 7Li(10C,10Bg) : proof of the principle Sasamoto et al. 1022 keVg-ray

  21. Search for IV-nonspin-MR in 90Zr Sasamoto et al.

  22. Summary • RI beam induced charge exchange (RICE) reactions can be tools toprobe 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.)

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