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Heavy-Ion Double Charge Exchange study via 12 C( 18 O, 18 Ne) 12 Be reaction

Heavy-Ion Double Charge Exchange study via 12 C( 18 O, 18 Ne) 12 Be reaction. Motonobu Takaki (CNS, The University of Tokyo)

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Heavy-Ion Double Charge Exchange study via 12 C( 18 O, 18 Ne) 12 Be reaction

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  1. Heavy-Ion Double Charge Exchange study via 12C(18O,18Ne)12Be reaction Motonobu Takaki (CNS, The University of Tokyo) H. Matsubara2, T. Uesaka3, N. Aoi4, M. Dozono1, T. Hashimoto4, T. Kawabata5, S. Kawase1, K. Kisamori1, Y. Kubota1, C.S. Lee1, J. Lee3, Y. Maeda6, S. Michimasa1,K. Miki4, S. Ota1, M. Sasano3, T. Suzuki4, K. Takahisa4, T.L. Tang1, A. Tamii4, H. Tokieda1, K. Yako1, R. Yokoyama1, J. Zenihiro3, and S. Shimoura1 1CNS, The University of Tokyo 2National Institute of Radiological Science (NIRS) 3RIKEN Nishina Center 4Research Center for Nuclear Physics, Osaka University 5Department of Physics, Kyoto University 6Department of Applied Physics, University of Miyazaki • 2nd conference on ARIS 2014, June 2nd 2014

  2. Double Charge eXchange (DCX) reaction • 12C(π-,π+)12Be • Probe for unstable nuclei • Using stable target with ΔTz = 2 • Powerful tool to investigateIV Double Giant Resonances • DIAS, DIVDR… • J.E. Ungar et al., PLB, 144 333 (1984) • S. Mordechai et al., PRL 60, 408 (1988).

  3. 1 • 30 HIDCX with Missing mass method at Intermediate energy • 12C(14C,14O)12Be • Elab=24A MeV • 20 • 24Mg(18O,18Ne)24Ne • at 76A MeV • 10 • 0 • 0 • Counts • Heavy-ion • Double Spin and/or Isospin flip (ΔS=2, ΔTz=2) • Missing mass method • measure All excitation energy regionon a same footing • Intermediate energy (~ 100MeV/u) • direct reaction process dominance • simple reaction mechanism • ΔL sensitivity of angular distributions • multipole assignment • d2σ/dΩc.m.dE (nb/sr/(0.5 MeV)) • Sn • J. Blomgren et al. • PLB, 362 34 (1995) • 25 20 15 10 5 0 Ex • W. Oertzen et al., • NPA, 588 129c (1995) • 0 • 5 • 10 • 15 • 20 • 24Ne excitation energy (MeV) • We performed 12C(18O,18Ne) reaction experiment • in normal kinematics at 80 MeV/nucleon.

  4. (18O,18Ne) reaction • B(GT) ~ 0.07 • B(GT)=0.11 • B(GT) ~ 0 • τ • τ • Ground states of 18O and 18Ne are among the same super-multiplet. • simple transition process • large transition probability • A primary 18O beam is employed • high intensity (> 10 pnA) • Experiment can be performed at RCNP with GR spectrometer • high quality data with high energy resolution • 18O • 18Ne • στ • στ • 18F • B(GT)=3.15 • B(GT)=1.05

  5. Setup of the experiment • 18Ne • ΔE in PL Scint. • Good PID resolution • Energy resolution = 1.2 MeV(FWHM) • A/Q • 1.7 • 1.8 • 1.9 • 2.0 • 2.1 • 2.2 • Grand Raiden • 18Ne • 12C target (2.2 mg/cm2) • 18O beam • beam: 18O • Energy: 80A MeV • ΔE: ~ 1 MeV • intensity: 25 pnA • Ring Cyclotron Facility, • Research Center for Nuclear Physics, • Osaka University • MWDCs and plastic scinti.

  6. Successful result • 2+/3- • Bound and unbound states were observed in one-shot measurement. • The 2.2 MeV peak has a larger cross section than the g.s. • Different angular distribution of the 4.5 MeV peak.

  7. Reaction calculation • Coupled-channel calculation with microscopic form factors • Shell model • double folding • coupled channel • one body transition density (OBTD) • form factors • diff. cross section (dσ/dθ) • SFO int. • USD int. • optical potential • global (double folding) • NN effective int. • (Love-Franey 100 MeV) • With appropriate normalizations, the experimental distributions were reproduced. • normalization factor=0.7 • normalization factor=1.3 • 0+ • 2+ • preliminary • preliminary • ΔL=0 • ΔL=2

  8. Probing of the configuration mixing Mixing degree between p- and sd-shell components in 0+ states of 12Be • The cross section for the two 0+ states at forward angle • dominated by double Gamow-Teller transition(ΔL=0, ΔS=2, ΔT=2). • mainly reflect the p-shell contribution. • } • sd • mixing • 1p1/2 • 1p3/2 • (p)2 dominance • 1s1/2 • proton • neutron • 12Be

  9. Evaluation of p-shell contribution to 0+ states of 12Be • Assumption: • 12C g.s. has only p-shell configuration. • The transition occurs in the 0hω • relative cross section between 0+g.s. and 0+2 • ←→ ratio of p-shell contributions • only statistical error • Similar spectroscopic value with earlier works • R. Meharchant et al., PRL 122501, 108 (2012) • H. T. Fortune et al., PRC, 024301, 74 (2006) • F. C. Barker, Journal of Physics G, 2(4), L45 (1976)

  10. Double Gamow-Teller transition • B(GT2) • This work: • B(GT2)values are derived from the OBTD with the normalization factor of the cross section. • Reference • 12C(0+) -> 12B(1+, g.s.) (I. Daito et al., PLB 418, 27 (1998).) • 12B(1+, g.s.) -> 12Be(0+) (R. Meharchand et al., PRL 108, 122501 (2012)) • very • preliminary • very • preliminary

  11. Conclusion • 2+/3- • The 2.2 MeV peak has a larger cross section than the g.s. • The p1/2 component dominantly contributes to the 0+2 state. • The different angular distribution of the 4.5 MeV peak • The HIDCX reaction can assign multipolarities.

  12. Summary • HIDCX reactions are unique probe for light unstable nuclei and IV double giant resonances, especially spin-flip excitations. • The HIDCX 12C(18O,18Ne) reaction experiment was performed. • Three clear peaks were observed at Ex=0.0, 2.2 and 4.5 MeV. • Larger cross section for the 12Be(0+2) state reflects the degree of the p-shell contribution for the two 0+ states in 12Be. • The different angular distributions of the cross sections suggesta sensitivity to multipolarities. • The microscopic calculation for the HIDCX was performed. • The cross section can be reproduced with the appropriate normalization factors. • B(GT)2 value is derived. • This study shows that spectroscopic studies with the HIDCX reaction are a valid and feasible! • Thank you for your attention.

  13. Backup • 12C(14C,14O)12Be • Elab=24A MeV • Counts • 12C(π+,π-)12O • Counts • Ex • 30 • 20 • 0 • 10 • S. Mordechai et al., • PRC, 32 999 (1985) • 25 20 15 10 5 0 Ex • W. Oertzen et al., • NPA, 588 129c (1995)

  14. Reaction calculation scheme • one-body transition density • single particle wave function • n-n effective interaction • transition density • double-folding transition form factor • coupled channel calculation

  15. 4.56 • 2+ • Target • Projectile • g.s. • 0+ • 18Ne (g.s., 0+) • 12Be • 7.7 • 1- • GT • 18F (g.s., 1+) • Calculate cross sections for various paths. • g.s. • 1+ • GT • 12B • 0+ • 18O (g.s., 0+) • 12C

  16. Configuration mixing of 0+ states in 12Be Mixing degree between p- and sd-shell components in 0+ states of 12Be • } • sd • mixing • 1p1/2 • 1p3/2 • (p)2 dominance • 1s1/2 • proton • neutron • 12Be • (sd)2 dominance

  17. decay time constant: 395+173 ns • ⇔ 331 ns in literature Test Experiment to prove experimental feasibility • -92 • 18O(12C,12Beγ)18Ne(gnd) • 2γ time spectrum • w/o γ-tag • Time [ns] • BG due to particle • mis-identification • 511keV • with γ-tag • ×10 • t • 12Be • 511keV

  18. Our experimental result • The cross section for the 0+2 state is larger than 0+1 (g.s.). • Double GT transitions dominate in two 0+ states. • → Sensitive to the 0ℏω configuration Dominance of double Gamow-Teller transition

  19. Single charge exchange reaction result

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