Proton resonance scattering of 7 Be H. Yamaguchi, Y. Wakabayashi, G. Amadio, S. Kubono, H. Fujikawa, A. Saito, J.J. He, T. Teranishi, Y.K. Kwon, Y. Togano, N. Iwasa, K. Inafuku, M. Niikura, and L.H. Khiem Center for Nuclear Study, Univ. of Tokyo, Kyushu University, RIKEN, Chung-Ang Univ. Rikkyo Univ., Tohoku Univ., IPE Introduction of CRIB Motivation of the measurement Method Result Summary

2006 Jun 29 Nuclei in the Cosmos IX CRIB Introduction CNS Radio Isotope Beam separator Low energy(<10MeV/u) RI beams, in-flight method Primary beam from K=70 AVF cyclotron Momentum (Magnetic rigidity) separation by “double achromatic” system, and velocity separation by a Wien filter. Orbit radius: 90 cm, solid angle: 5.6 msr, momentum resolution: 1/850.

2006 Jun 29 Nuclei in the Cosmos IX Low-Energy RI beam Productions at CRIB Reactions such as (p,n), (d,p) and ( 3 He,n) in inverse kinematics are used. RI beamPrimary beamReactionCross sectio n TargetIntensity 10 C 6.1 A MeV 10 B(4+) 7.8 A MeV (200 pnA) p( 10 B, 10 C)n2 mbCH 4 gas 1.3 mg/cm 2 (1.6  10 5 pps) 14 O 6.7 A MeV 14 N(6+) 8.4 A MeV (500 pnA) p( 14 N, 14 O)n8 mbCH 4 gas 1.3 mg/cm 2 (1.7  10 6 pps) 12 N 3.9 A MeV 10 B(4+) 7.8 A MeV 200 pnA 3 He( 10 B, 12 N)n5 mb 3 He gas 0.25 mg/cm  10 3 pps 11 C 3.4 A MeV 10 B(4+) 7.8 A MeV 200 pnA 3 He( 10 B, 12 N * )n 12 N*  11 C+p  20 mb 3 He gas 0.25 mg/cm  10 4 pps Other RI beams have been produced at CRIB: 7 Be, 8 Li, 13 N, 17 N, 18 F, 21 Na, 22 Mg, 23 Mg, 25 Al, 26 Si, 39 Ar,… typically pps

2006 Jun 29 Nuclei in the Cosmos IX low-T production target Features: Lq. N 2 cooling for a better cooling power (~100 W) and thicker target. Forced target gas flow (30 l/min) for an efficient cooling of the gas. Oxygen density monitoring

2006 Jun 29 Nuclei in the Cosmos IX Recent experiments at CRIB ( ) 39 Ar production for its lifetime (~269 y) measurement geochemical studies, distribution of cosmic ray that produces 39 Ar. 8 Li( , n ) 11 B Primordial nuclear synthesis in big bang model. 25 Al+ p resonance scattaring Production of 26 Si in explosive hydrogen burning. 7 Be+ p resonance scattaring Related to 7 Be( p,  ) 8 B reaction and astrophysical S-factor S 17 (E). 8 B’s 2 - state and higher excited states. 8 Li+ p resonance scattaring Nuclear structure and isotope shift 16 N, 18 N polarized beam production Intense 7 Be beam production by Lq.N 2 -cooled gas target For the direct measurement of 7 Be( p,  ) 8 B reaction Beam production by 40 Ca+ 12 C fusion reaction ….and some more experiments are in the test phase. Collaborating with ATOMKI, McMaster U, INFN (Catania), ANU, Chung- Ang U, Ewha U., VAST(Vietnam), RIKEN, Kyushu U., TITech,...

2006 Jun 29 Nuclei in the Cosmos IX 7 Be+p resonance scattering; Motivation (I) Astrophysically important reaction: 7 Be(p,  ) 8 B 8 B neutrino … high energy (10MeV), the largest component detected by most of the major neutrino detectors in the world. Astrophysical S-factor S 17 (0)…determined by 7 Be(p,  ) 8 B cross section. For a direct measurement of the above reaction in inv. kinematics Intense 7 Be Beam production 8 B structure may affect the results S 17 (0)= (keV b) (recommended value by Adelberger et al., 1997)

2006 Jun 29 Nuclei in the Cosmos IX Motivation ( II ) Nuclear synthesis Usually, triple-  process is important to pass over the instability at A=8. Reaction path through 7 Be might be important in special environments (e.g. high-temperature and metal-deficient stars).

2006 Jun 29 Nuclei in the Cosmos IX Motivation ( III ) Study the structure of 8 Ｂ States at 0.77 MeV and 2.32 MeV are well known, but no clear knowledge above 3.5 MeV. A wide (>4 MeV) state at 3.5 MeV …2 - ; low-lying 2s state? the resonance may contribute to the cross section even at 0 energy (3% of on resonance). V.Z. Gol’dberg et al, JETP Lett. (1998), another measurement in G.V. Rogachev et al, Phys. Rev. C (2001).

2006 Jun 29 Nuclei in the Cosmos IX Method (RI beam production) Primary beam: 7 Li 3+,8.76 MeV/u (61.9 MeV), ~100 pnA Production target: Hydrogen gas (0.67 mg/cm 2 ), 7 Li 3+ (p, n) 7 Be 4+. Secondary beam: 7 Be 4+, 53.8 MeV secondary target) 3 x 10 5 pps.

2006 Jun 29 Nuclei in the Cosmos IX Method (Experimental setup) Thick target method: all the 7 Be were stopped in the CH 2 target, and recoil protons ( Emax=23 MeV ) were detected by silicon detector telescopes (60 msr x 4 sets, covering up to 45 degree). E proton ⇒ E cm ⇒ E ex

2006 Jun 29 Nuclei in the Cosmos IX Experimental Setup (picture)

2006 Jun 29 Nuclei in the Cosmos IX Advantages over past measurements Wide energy range Ecm up to 6.7 MeV (< 3.5MeV in the past measurements). Wide angle 0-45 degree in  LAB (fixed angles in the past). Inelastic scattering 7 Be(p,p) 7 Be* Inelastic events to the 7 Be excited state at 429 keV may affect the measurements. NaI detectors were used to detect 429 keV gamma rays.

2006 Jun 29 Nuclei in the Cosmos IX Result (RI beam production) PI by TOF and energy: 7 Be was clearly identified. The measurement (left) and calculation (right) were in good agreement. Purity 56% (above figure, before the Wien Filter), 100% (after the Wien filter with high voltages of ±40 kV). Intense 7 Be 4+ beam was successfully produced (3 x 10 5 pps). F0-F2 TOF(ns) Particle Energy(MeV)

2006 Jun 29 Nuclei in the Cosmos IX Selection of proton events Proton was the largest component and colud be identified by the  E-E relationship. Considerable amount of 3 He and 4 He are also seen (break up of 7 Be?).

2006 Jun 29 Nuclei in the Cosmos IX Carbon background subtraction Preliminary

2006 Jun 29 Nuclei in the Cosmos IX Cross section spectrum (  LAB =0~5 deg) Cross section spectrum (  LAB =0~5 deg) Good agreement with Rogachev et al. (2001), for the energies around the 2.3 MeV resonance. Wide state expected at 3.5 MeV was not clearly seen (so far). Indication of a new state around E ex =4.6 MeV. Preliminary

2006 Jun 29 Nuclei in the Cosmos IX Resonance parameters We can make sure the spin and parity by analyzing the angular distribution. Contribution from inelastic scattering, three- body decay, and so on must be considered. R-matrix analysis… resonance parameters can be deduced by the resonance shape in the excitation function. Preliminary results (assuming continuum b.g.): E~4.7 MeV,  keV Spin, parity 0 - (or 1 - ) fits better than 1 +, 3 + and 4 +, which were identified in the mirror nucleus ( 8 Li). E, ,J  of 8 Li levels: 3.21 MeV, ~1000 keV, MeV, ~650 keV, (0,1) MeV, ~1000 keV, MeV, 35 keV, ?

2006 Jun 29 Nuclei in the Cosmos IX Summary and future analysis For the future: Complete spin, parity etc. determination by the R- matrix analysis. Analysis for the angular distribution. Consideration of inelastic events by the NaI data. We have measured proton elastic scatterings of 7 Be with thick target method, using 7 Be 4+ beam produced in CRIB facilty (CNS, Univ. of Tokyo). Cross section spectrum against center-of-mass energy was obtained for  LAB  deg. (  CM  deg.). Cross section is in good agreement with the past measurements for the energy region of 1~2.5MeV. Indication of a new state of 8 B is seen at E ex ~4.7 MeV.