Inelastic scattering of 15 B and 17 B Y. Kondo A , T. Nakamura A , N. - PowerPoint PPT Presentation

Inelastic scattering of 15 B and 17 B Y. Kondo A , T. Nakamura A , N. Fukuda B , T. Sugimoto A , M. Miura A , N. Aoi B , H. Baba C , D. Bazin D , T. Gomi C , H. Hasegawa C , N. Imai B , T. Kobayashi E , T. Kubo B , T. Motobayashi B , A. Saito C , H. Sakurai F , S. Shimoura G , K. Watanabe E , Y. X. Watanabe H , T. Yakushiji E , Y. Yanagisawa B , K. Yoneda D , and M. Ishihara B A: Department of Physics, Tokyo Institute of Technology, Tokyo 152--8551, Japan B: RIKEN (Institute of Physical and Chemical Research, Saitama 351--0198, Japan C: Department of Physics, Rikkyo University, Tokyo 171--8501, Japan D: National Superconducting Cyclotron Laboratory, Michigan State University, Michigan 48824--1321, U.S.A E: Department of Physics, Tohoku University, Miyagi 980--8578, Japan F: Department of Physics, University of Tokyo, Tokyo 113--0033, Japan G: Center for Nuclear Study, University of Tokyo, Saitama 351--0198, Japan H: High Energy Accelerator Research Organization (KEK), Ibaraki 305--0801, Japan

Exotic features of neutron rich B isotopes 11 B n 13 B 15 B n 15 B 17 B Neutron halo structure of 17 B 19 B A. Ozawa et al. Phys. Lett. B, 334 , 18, (1994). T. Suzuki et al. Nucl. Phys. A, 658 , 313, (1999). T. Suzuki et al. Phys. Rev. Lett., 89 , 12501, (2002). Clustering structure Y. Kanada-En’yo and H. Horiuchi. Phys. Rev. C, 52 , 647, (1995).

Energy level of 15 B Experiment [14] M. A. Hotchkis et al. Nucl. Phys. A398 , 130, (1983). [15] T.S. Bhatia et al. Phys. Lett., 76B , 562, (1978). [13] R. Kalpakchieva et al. Eur. Phys. J. A, 7 , 451, (2000). 13 C( 14 C, 12 N) 15 B reaction Theory [16] N.A.F.M. Poppelier et al. Phys. Lett., 157B , 120, (1985). [17] E. K. Warburton and B. A. Brown. Phys. Rev. C, 46 , 923, (1992). No bound excited states of 15 B are known. [12] Y. Kanada-En’yo and H. Horiuchi. Phys. Rev. C, 52 , 647, (1995). No excited states of 17 B are known.

Experiment Inelastic scattering on C, Pb target C( 15 B, 15 B * ), Pb( 15 B, 15 B * ), C( 17 B, 17 B * ), Pb( 17 B, 17 B * ) C θ 15 B ’ E γ 15 B* 15 B ☯ Energy of gamma ray Excitation energy (Doppler shift should be corrected.) ☯ Ratio of cross section ( σ Pb / σ C ) Multipolarity 1 - or 2 + ? ☯ Angular distribution (C target) Multipolarity 1 - or 2 + ? Deformation length ( δ = β R )

Experimental setup Neutron counters (not used) Veto counters (not used) Dipole magnet Drift chamber (FDC1) (not used) Hodoscope NaI(Tl) scintillators Drift chamber (FDC3) PPACs 15 B, 17 B 15 B, 17 B 73 Mev/u Secondary target (C, Pb)

Energy spectrum (C target) (Doppler shift was corrected) 1.07 MeV 1.34 MeV C( 17 B, 17 B * ) C( 15 B, 15 B * ) These are the first observation. These correspond to the first excited states.

Observed gamma rays using C target nuclide reaction This work Previous work 17 B C( 17 B, 17 B) 1.07(1) 15 B C( 17 B, 15 B) 1.34(1) C( 15 B, 15 B) 1.35(1) 14 B C( 17 B, 14 B) 0.652(2) 0.740(40) [37] C( 15 B, 14 B) 0.655(3) 12 B C( 17 B, 12 B) 0.953(4) 0.95310(60) [38] 1.66(1) 1.67352(60) [38] 0.957(4) 0.95310(60) [38] C( 15 B, 12 B) 1.68(2) 1.67352(60) [38] [37] G. C. Ball et al. Phys. Rev. Lett., 31 , 395, (1973). 14 C( 7 Li, 7 Be) 14 B [38] H. H. Williams et al. Phys. Rev., 144 , 801, (1966). 11 B( d , p ) 12 B γ

Energy level of 15 B and 17 B [16,17] shell model [12] AMD model (Clustering structure) [40] G. Audi et al. Nucl. Phys. A, 624 , 1, (1997).

Energy spectrum (Pb target) Pb( 17 B, 17 B * ) Pb( 15 B, 15 B * )

Cross section of inelastic scattering 15 B 17 B 1 - → σ (Pb) / σ (C) ～ 100 σ (C) [mb] 17.0(1.1) 11.9(6) 2 + → σ (Pb) / σ (C) ～ 2-3 σ (Pb) [mb] < 190 < 160 σ (Pb) / σ (C) < 11 < 13 UPPER LIMIT OF PEAK AREA O. Helene. Nucl. Instrum. Methods, 212 , 319, (1983).

Angular distribution Calculation using ECIS with assumptions 2 + transition Spin-parity of the excited state is 5/2 - Collective excitation model → rotational model Optical potential (A: 12 C- 12 C [24], B: 16 O- 12 C [39]) [24] M. Buenerd et al. Nucl. Phys. A424 , 313, (1984). [39] Maria-Ester Brandan. Phys. Rev. Lett., 60 , 784, (1988).

Deformation length ( δ＝β R) Deformation length [fm] 15 B 17 B Optical potential A 1.64(6) 1.35(3) Optical potential B 1.47(6) 1.24(2) δ（ １５ B ）＞δ（ １７ B ） The deformation of 15 B seems to be larger than 17 B.

Summary Inelastic scattering on C, Pb target C( 15 B, 15 B * ), Pb( 15 B, 15 B * ), C( 17 B, 17 B * ), Pb( 17 B, 17 B * ) Gamma-ray energy 15 B: E X = 1.34 MeV Observed for the first time 17 B: E X = 1.07 MeV 14 B: E X = 0.65 MeV revised Cross section ratio Angular distribution 2 + transition (mixing of 1 + transition is still unknown.) Angular distribution δ ( 15 B) > δ ( 17 B)

Introduction Vanishing of magic number N =20 (Island of inversion) Al Mg Na Proton number Ne F 8 O 15 B, 17 B N C stable B Be neutron rich Li Vanishing of 2 He magic number N =8 proton rich H 2 8 20 Neutron number n 15 B n Neutron halo Clustering structure

In-beam gamma-ray spectroscopy ex. inelastic scattering of 15 B Excited state C target ’ C E γ E γ Ground state ＊ Θ ’ 15 B 15 B 15 B β projectile ｖ β＝ Doppler correction ｃ − β θ ' 1 cos = = E β ( 0 . 38 ) ' E γ γ − β 2 1 Particle frame Lab frame

RIPS （ RI KEN P rojectile-fragment S eparator) 22 Ne 110 MeV/u 15 B Primary target 72 MeV/u (Be) 12 kcps 17 B 73 MeV/u 0.8 kcps Plastic scintillator

Particle identification Incident particle TOF, pulse height ( Z 2 / v 2 ) Outgoing particle Z (charge) TOF, pulse height ( Z 2 / v 2 ) A (mass) Rigidity ( Av / Z ), TOF, Z

Particle identification of incident particle

Particle identification of outgoing particle

Magnetic moment of B isotopes