Presentation on theme: "Heavy-Ion Double Charge Exchange study via 12 C( 18 O, 18 Ne) 12 Be reaction Motonobu Takaki (CNS, The University of Tokyo) H. Matsubara 2, T. Uesaka 3,"— Presentation transcript:
Heavy-Ion Double Charge Exchange study via 12 C( 18 O, 18 Ne) 12 Be reaction Motonobu Takaki (CNS, The University of Tokyo) H. Matsubara 2, T. Uesaka 3, N. Aoi 4, M. Dozono 1, T. Hashimoto 4, T. Kawabata 5, S. Kawase 1, K. Kisamori 1, Y. Kubota 1, C.S. Lee 1, J. Lee 3, Y. Maeda 6, S. Michimasa 1, K. Miki 4, S. Ota 1, M. Sasano 3, T. Suzuki 4, K. Takahisa 4, T.L. Tang 1, A. Tamii 4, H. Tokieda 1, K. Yako 1, R. Yokoyama 1, J. Zenihiro 3, and S. Shimoura 1 1 CNS, The University of Tokyo 2 National Institute of Radiological Science (NIRS) 3 RIKEN Nishina Center 4 Research Center for Nuclear Physics, Osaka University 5 Department of Physics, Kyoto University 6 Department of Applied Physics, University of Miyazaki 2 nd conference on ARIS 2014, June 2 nd 2014
Double Charge eXchange (DCX) reaction Probe for unstable nuclei Using stable target with ΔT z = 2 Powerful tool to investigate IV Double Giant Resonances DIAS, DIVDR… 2 12 C(π -,π + ) 12 Be J.E. Ungar et al., PLB, (1984) S. Mordechai et al., PRL 60, 408 (1988).
HIDCX with Missing mass method at Intermediate energy Heavy-ion Double Spin and/or Isospin flip (ΔS=2, ΔT z =2) Missing mass method measure All excitation energy region on a same footing Intermediate energy (~ 100MeV/u) direct reaction process dominance -simple reaction mechanism ΔL sensitivity of angular distributions -multipole assignment 3 Counts Ex 12 C( 14 C, 14 O) 12 Be E lab =24A MeV W. Oertzen et al., NPA, c (1995) 24 Mg( 18 O, 18 Ne) 24 Ne at 76A MeV d 2 σ/dΩ c.m. dE (nb/sr/(0.5 MeV)) Ne excitation energy (MeV) J. Blomgren et al. PLB, (1995) We performed 12 C( 18 O, 18 Ne) reaction experiment in normal kinematics at 80 MeV/nucleon. SnSn
( 18 O, 18 Ne) reaction Ground states of 18 O and 18 Ne are among the same super-multiplet. simple transition process large transition probability A primary 18 O beam is employed high intensity (> 10 pnA) Experiment can be performed at RCNP with GR spectrometer high quality data with high energy resolution 4 τ τ στ B(GT)=3.15 B(GT)= O 18 F 18 Ne B(GT)=0.11 B(GT) ~ 0.07 B(GT) ~ 0
Setup of the experiment 5 12 C target (2.2 mg/cm 2 ) MWDCs and plastic scinti. 18 O beam beam: 18 O Energy: 80A MeV ΔE: ~ 1 MeV intensity: 25 pnA Ring Cyclotron Facility, Research Center for Nuclear Physics, Osaka University Grand Raiden Energy resolution = 1.2 MeV(FWHM) A/Q ΔE in PL Scint. 18 Ne Good PID resolution
Successful result 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 /3 -
Coupled-channel calculation with microscopic form factors Reaction calculation preliminary one body transition density (OBTD) form factorsdiff. cross section (dσ/dθ) Shell modeldouble foldingcoupled channel NN effective int. (Love-Franey 100 MeV) SFO int. USD int. optical potential global (double folding) normalization factor=0.7normalization factor=1.3 ΔL=0ΔL=2 With appropriate normalizations, the experimental distributions were reproduced.
Probing of the configuration mixing Mixing degree between p- and sd-shell components in 0 + states of 12 Be 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 1p 3/2 1s 1/2 1p 1/2 } mixing 12 Be protonneutron 8 (p) 2 dominance
Evaluation of p-shell contribution to 0 + states of 12 Be p-shell contribution in 0 + g.s. and g.s. (%)0 + 2 (%)0 + 2 /0 + g.s. methods Meharchant ± B( 7 Li, 7 Be) Fortune SM Barker SM R. Meharchant et al., PRL , 108 (2012) H. T. Fortune et al., PRC, , 74 (2006) F. C. Barker, Journal of Physics G, 2(4), L45 (1976) relative cross section between 0 + g.s. and ←→ ratio of p-shell contributions Similar spectroscopic value with earlier works 9 Assumption: C g.s. has only p-shell configuration. 2. The transition occurs in the 0hω only statistical error
Double Gamow-Teller transition B(GT 2 ) This work: -B(GT 2 ) values are derived from the OBTD with the normalization factor of the cross section. Reference - 12 C(0 + ) -> 12 B(1 +, g.s.) (I. Daito et al., PLB 418, 27 (1998).) - 12 B(1 +, g.s.) -> 12 Be(0 + ) (R. Meharchand et al., PRL 108, (2012)) Be(0 +, g.s.) 1st2nd B(GT) B(GT 2 ) This work0.17±0.04 Reference0.999± ± ± Be(0 + 2 ) 1st2nd B(GT) B(GT 2 ) This work0.27±0.07 Reference0.999± ± ±0.05 very preliminary very preliminary
Conclusion The 2.2 MeV peak has a larger cross section than the g.s. The p1/2 component dominantly contributes to the state. The different angular distribution of the 4.5 MeV peak The HIDCX reaction can assign multipolarities /3 -
Summary HIDCX reactions are unique probe for light unstable nuclei and IV double giant resonances, especially spin-flip excitations. The HIDCX 12 C( 18 O, 18 Ne) reaction experiment was performed. Three clear peaks were observed at Ex=0.0, 2.2 and 4.5 MeV. Larger cross section for the 12 Be(0 + 2 ) state reflects the degree of the p-shell contribution for the two 0 + states in 12 Be. The different angular distributions of the cross sections suggest a 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.
Backup C(π +,π - ) 12 O S. Mordechai et al., PRC, (1985) Ex Counts Ex 12 C( 14 C, 14 O) 12 Be E lab =24A MeV W. Oertzen et al., NPA, c (1995)
Reaction calculation scheme 14 single particle wave function one-body transition density n-n effective interaction double-folding transition form factor transition density coupled channel calculation
Calculate cross sections for various paths. 12 C 12 B 12 Be g.s g.s. 7.7 TargetProjectile 18 Ne (g.s., 0 + ) 18 O (g.s., 0 + ) 18 F (g.s., 1 + ) GT
Mixing degree between p- and sd-shell components in 0 + states of 12 Be Configuration mixing of 0 + states in 12 Be sd 1p 3/2 1s 1/2 1p 1/2 } mixing 12 Be protonneutron (p) 2 dominance (sd) 2 dominance 16 p-shell contribution in 0 + g.s. and g.s. (%)0 + 2 (%)0 + 2 /0 + g.s. methods Meharchant ± B( 7 Li, 7 Be) Fortune SM Barker SM
Test Experiment to prove experimental feasibility 511keV 12 Be t BG due to particle mis-identification with γ-tag ×10 w/o γ-tag 18 O( 12 C, 12 Beγ) 18 Ne(gnd) 2γ time spectrum Time [ns] decay time constant: ns ⇔ 331 ns in literature -92
Dominance of double Gamow-Teller transition The cross section for the state is larger than (g.s.). Double GT transitions dominate in two 0 + states. → Sensitive to the 0 ℏ ω configuration Our experimental result