1. Low-lying states in 11 B Center for Nuclear Study, University of Tokyo KAWABATA Takahiro RCNP, Osaka UniversityH. Fujimura, M. Fujiwara, K. Hara, K. Hatanaka, M. Itoh, J. Kamiya, A. Tamii, M. Uchida, H.P. Yoshida Department of Physics, Kyoto University T. Ishikawa, M.. Nakamura, H. Sakaguchi, H. Takeda, Y. Yasuda, M. Yosoi Department of Physics, Konan University H. Akimune, K. Y. Hara Department of Physics, Kyushu University T. Noro, T. Wakasa SPring-8H. Toyokawa Department of Physics, Osaka University H. Fujita, Y. Fujita, Y. Shimbara, H. Ueno

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

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

4. Experiment Experiment was performed at RCNP, Osaka University. 11 B( 3 He, t) RCNP-E114 E= 450 MeV,  lab = 0˚~14˚ - d  /d  11 B(d,d’) RCNP-E200 E= 200 MeV,  lab = 0˚~25˚ - d  /d , A y, A yy 11 B(p, p’) RCNP-E137 E=392 MeV,  lab = 2˚~14˚ - d  /d , A y, P, D NN

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

6. B(GT) from ( 3 He,t) reactions E x (MeV) B(GT) Exp (R 2 =8.24) B(GT) Exp (R 2 =5.24) 0.000 (3/2  )0.345±0.008 2.125 (1/2  )0.401±0.0320.461±0.026 4.445 (5/2  )0.453±0.0290.521±0.031 5.020 (3/2  )0.487±0.0290.551±0.036 8.104 (3/2  )  0.003  0.004 8.420 (5/2  )0.398±0.0310.466±0.045 B(GT) for excited states were obtained from DWBA analysis. Choice of the R 2 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 12 C(d, d’) is used as a reference for  J decomposition. E x (MeV) B(  ) Exp 2.120.040±0.006 4.44-------- 5.020.043±0.008 8.920.016±0.004 B(  )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 ( 3 He,t) Blue … No parameters adjusted. Describe experimental results except D NN Red … Best fit. D NN is sensitive to the mixing angle  m.

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

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

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