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Low-lying states in 11 B

Low-lying states in 11 B. Center for Nuclear Study, University of Tokyo KAWABATA Takahiro. Introduction. M1 (GT) strengths provide important information on the nuclear structure. Isovector ( D T=1) transitions were extensively studied,

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Low-lying states in 11 B

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  1. Low-lying states in 11B Center for Nuclear Study, University of Tokyo KAWABATA Takahiro

  2. Introduction M1 (GT) strengths provide important information on the nuclear structure. Isovector (DT=1) transitions were extensively studied, but there are few data on isoscalar (DT=0) component. • A=11 mirror system.- M1 and GT transitions. • Non-zero g.s. isospin.- Both DT=1 and DT=0 exist. • Promising neutrino detection material.- Selectivity for neand nx.- Detection by one setup at one time.R.S. Raghavan et al., Phys. Rev. Lett. 57, 1801 (1989).

  3. Hadron Scattering Hadron scattering is a good measure for nuclear matrix elements. Simple reaction mechanism - Good linearity between ds/dW and B(ô). Selectivity for the DT = 1 and DT = 0 components. Spin observables give a good measure to separate DJp and DT. (3He, t) … DT = 1 only (DTz = -1) (d, d’) … DT=0 only (DTz =0) (p, p’) … DT = 1 and DT = 0 (DTz = 0) We measured the three reactions to decompose the excitation modes.

  4. Experiment Experiment was performed at RCNP, Osaka University. 11B(3He, t) RCNP-E114 E= 450 MeV, qlab= 0˚~14˚ - ds/dW 11B(d,d’) RCNP-E200E= 200 MeV, qlab= 0˚~25˚- ds/dW, Ay, Ayy 11B(p, p’) RCNP-E137E=392 MeV, qlab= 2˚~14˚- ds/dW, Ay, P, DNN

  5. Charge Exchange Reactions Charge exchange reaction provides B(GT) values. R2= |Vst/Vs|2 is a key ingredient for B(GT) determination. R2=8.24 (11) is widely used for (3He,t) reaction at 450 MeV. FL int. suggests a smaller value R2=5.24 for A=11 system.

  6. B(GT) from (3He,t) reactions B(GT) for excited states were obtained from DWBA analysis. Choice of the R2 value changes 15% normalization.

  7. Elastic and inelastic deuteron scattering • Optical model parameters were determined for the macroscopic analysis. - Modify the optical potential to obtain a reasonable description on the 2+ transition. - Replace q by 0.78q for the 0+ transition. • Fit the 1+ transition by the spherical Bessel function.

  8. Deuteron Inelastic Scattering 12C(d, d’) is used as a reference for DJ decomposition. • B(s)s for 2.12 and 5.02-MeV states were successfully extracted. • B(E2) for 4.44-MeV state is strong and obscures the M1 strength. • 8.56 MeV seems to be a cluster state.

  9. Proton Inelastic Scattering DWBA calculation- Franey-Love -H.O. single particle state - Strengths from (d,d’) and (3He,t) Blue … No parameters adjusted. Describe experimental results except DNN Red … Best fit. DNN is sensitive to the mixing angle qm.

  10. Comparison with Shell model Measured B(st) and B(s) are compared with SM calculation. Experiment Yellow .. From (3He, t) and (d, d’) Red .. From (p, p’) with Franey-Love Gray .. From g-decay width(2.12-MeV state only) Shell modelBlack .. Cohen-Kurath (CKPOT, 0ħw)Red .. Fujimoto-Otsuka (2ħw) B(st): no problem. (3He, t) and (d,d’) results are consistent with g-decay result. B(s) for 2.12 and 5.02 strongly suppressed in the (p, p’) result..- uncertainty in the DWIA calculation ??

  11. Test of DWBA calculation Black … Franey-Love 425 MeV Blue … Franey-Love-Tamii 425 MeV(Modify Vs and Vst using 12C(p,p’) data.) Red … Melbourne (Density dependent) • FL and FLT provide good description. • ML is less reliable.

  12. Summary • M1 transition strengths in 11B are studied by measuring the 11B(3He,t), 11B(d, d’), and 11B(p, p’) reactions. • B(GT) is obtained from the 11B(3He, t) cross section. • B(s) for 2.12 and 5.02-MeV states were successfully obtained from the 11B(d, d’) data. - (3He, t) and (d, d’) are consistent with g-decay results • B(st) from (p, p’) is good, but B(s) ….. - Systematic uncertainty on B(s) is very large.

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