Reaction cross sections of 14 B and 8

Reaction cross sections of 14 B and 8 He on proton target for the separation of proton and neutron density distributions M. Tanaka, Osaka Univ. , Japan Osaka Univ. M. Fukuda, K. Matsuta, M. Mihara, Y. Morita, Y. Kamisho, J. Oono, R. Kanbe, S. Yamaoka, K. Watanabe Tokyo Univ. Sci. D. Nisimura, S. Kinno, Y. Taguchi Niigata Univ. M. Takechi, T. Ohtsubo, T. Izumikawa, A. Honma, D. Murooka National Institute of Radiological Science (NIRS) Saitama Univ. S. Suzuki, A. Kitagawa, M. Fukuda, T. Suzuki, T. Yamaguchi, J. Kouno, S. Sato S. Yamaki, S. Matsunaga

σR on proton target σNN has high sensitivity to the surface structure of nucleus at Intermediate energy region. Nucleon-nucleon total cross section σNN (＊) σpn＞σpp(nn) p-n asymmetry 〜 3 times Proton ＊(http: //pdg. lbl. gov/2010/hadronic-xsections/hadron. html) Sensitive to the composition of surface Proton target (Largest p-n asymmetry)

Neutron rich nucleus 14 B Magnetic moment [1] Q moment [2] 1 n removal reaction [3, 4] (14 B→ 13 B+n) These data point out large contribution of 2 s 1/2 orbit. S 1 n= 0. 970(21)Me. V [5] so small Halo nucleus 1 d 2 s 1/2 5/2 2 s 1/2 1 d 5/2 1 p 1/2 1 p 3/2 Proton 1 s 1/2 14 B Neutron [1] H. Okuno et al. , Phys. Lett. B 354, 41 (1995). [2] H. Izumi et al. , Phys. Lett. B 366, 51 (1996). [3] D. Bazin et al. , Phys. Rev. C 57, 2156 (1998). [4] V. Guimara es et al. , Phys. Rev. C 61, 064609 (2000). [5] G. Audi and A. H. Wapstra, Nucl. Phys. A 565 (1993).

Neutron rich nucleus 8 He σI at high energy [*] (790 Me. V/nucleon) Elastic Scattering [**] Large neutron radius Nucleon density distribution of 8 He [**] Structure ? [*] ] I. Tanihata, et al. , Phys. Lett. B 160 (1985) 380 -384. [**] A. A. Korsheninnikov, et al. , Nuclear Phys. A 617 (1997) 45 -56.

Purpose of this study Measurement of the σR for 8 He and 14 B ① on nucleus targets ② on proton targets at intermediate energies Obtaining the information of proton and neutron density distributions respectively from σR on nucleus and proton targets.

Production Target(F 0) Set up HIMAC in Chiba (Japan) SB 2 Course D 1 Beam F 1 PL Upstream Slit 14 B 130, 110, 85, 60 Me. V/nucleon Primary beam 18 O, 15 N 160 AMe. V F 0 Target Be 3. 0, 0. 55 g/cm 2 125, 110, 80, 65 Me. V/nucleon Primary beam 11 B 160 AMe. V F 0 Target Be 3. 7, 9. 2 g/cm 2 Measurement of σR Transmission method Reaction target: Be, C, Al, CH 2 Proton=(CH 2 − C)/2 D 2 Slit At F 3 Focal Plane 8 He Degrader Go to F 3 focal plane Bρ − TOF − ΔE TOF F 1 PL ΔE ΔE F 3 PL Cs. I(Tl) VETO Si PPAC Reaction Target ΔE − E E Na. I(Tl)

Glauber calculation Obtain this information Nucleon-Nucleon Density distribution total cross section (＊) of projectile nucleus. Nucleon-nucleon total cross section σ (＊) (Model density) Density distribution of target nucleus NN Nucleus target Proton target ρ N of 14 B, 8 He ρ n, ρ p of 14 B, 8 He with Modified Optical Limit approximation. ＊(http: //pdg. lbl. gov/2010/hadronic-xsections/hadron. html)

Derivation of proton and neutron density distributions ρ p, ρ n χ2 fitting with the width of ρ p as a free parameter. ρ n is deduced by subtraction. ρ n=ρ N− ρ p ρ Nucleon From σR on nucleus target

σR(E) on nucleus target ρ p and ρ n of 8 He ρ p(R) and ρ N(R) σI @ LBL [*] σR(E) on proton target [*] I. Tanihata, et al. , Phys. Lett. B 160 (1985) 380 -384

σR(E) on nucleus target ρ p and ρ n of 14 B ρ p(R) and ρ N(R) σI @ LBL [*] σR(E) on proton target Neutron tail [*] I. Tanihata, et al. , Phys. Lett. B 206 (1988) 592 -596

8 He root mean square radii Rproton, Rneutron, Rmatter [1] I. Tanihata et al. , Phys. Lett. B 289, (1992) 261 -266. [2] G. D. Alkhazov et al. , Nucl. Phys. A. 712, (2002) 269 -299 [3] M. Puchalski et al. , Hyperfine Interact (2010) 196: 35 -42 [4] R. Baldik et al. , Phys. of Atomic Nuclei (2010) Vol. 73, No. 1 74 -80

14 B root mean square radii Rproton, Rneutron, Rmatter Preliminary [2] A. Bhagwat et al. , Eur. Phys. J. A. 8, 511 -520 (2000) [3] H. Takemoto et al. Phys. Rev. C. 63. 034615

Summary • We measured σR for 8 He and 14 B on nucleus and proton targets at the HIMAC heavy ion synchrotron facility. • ρ p and ρ n were separated successfully through the χ2 fitting procedure with the modified Glauber calculation. • Rp, Rn, Rmatter were derived from ρ p, ρ n and ρ N. • As a future prospect, we will finalize the data analysis. And we deduce more accurate ρ p, ρ n of 8 He and 14 B, then make a detailed discussion on their structures.

Sub

Relation between Reaction cross section(σR) and density distribution Energy dependence of σR on Nucleus target p-n symmetric target σR Nucleon density distribution ρN It is impossible to clarify a composition of the surface by means of σR on p-n symmetric target. High energy →The inner part of nucleus Low energy →The outer part of nucleus

Measurement of σR 〜Transmission method〜 Detector１ Reaction target Detector２ Non-reacted particles Incident particles N 1 in N 2 in Target thickness t Reation target Detector１ Detector２ out Incident partices N 1 out Non-reacted particles N 2 out Correction for reactions in the detector.

ρN of 8 He The core is not a “bare” 6 He. (6 He is a halo nucleus. ) Best Fit Core: Z=2, N=4 Tail: 2 nucleons (1 p 3/2 orbit) S 2 n=2. 14 Me. V Best Fit is 1 p 3/2 2 nucleon with B. E= 3 Me. V

Single particle density calculation Binding Energy Calculate SP density with adjusting the potential depth to reproduce Binding energy. Best Fit Results 14 B 2 s 1/2 orbit with B. E=0. 97 Me. V (consistent with S 1 n=0. 97 Me. V) Woods-Saxon Coulomb Centrifugal Potential 8 He 1 p 3/2 orbit with B. E=3 Me. V (inconsistent with S 1 n=3 Me. V)

14 B Comparison between Exp. and Calc. value Tail Neutron or Proton Orbit 2 s 1/2 or 1 d 5/2

σR for 8 He on nucleus targets σI @ LBL (Tanihata et al. ) Preliminary [*] I. Tanihata, et al. , Phys. Lett. B 160 (1985) 380 -384.

σR for 8 He on proton targets σRH=(σICH 2−σIC)/2

σR on proton target Determined by subtracting the σIC from σICH 2. CH 2 : Polyethylene Measurement of interaction cross section σI on C, CH 2 targets.

σI for 14 B, 8 He on C, CH 2 targets.