G. Amadio

Low-lying non-normal parity states in 8B measured by proton elastic scattering on 7Be

Abstract A new measurement of proton resonance scattering on 7Be was performed up to the center-of-mass energy of 6.7 MeV using the low-energy RI beam facility CRIB (CNS Radioactive Ion Beam separator) at the Center for Nuclear Study of the University of Tokyo. The excitation function of Be 7 + p elastic scattering above 3.5 MeV was measured successfully for the first time, providing important information about the resonance structure of the 8B nucleus. The resonances are related to the reaction rate of 7Be( p , γ )8B, which is the key reaction in solar 8B neutrino production. Evidence for the presence of two negative parity states is presented. One of them is a 2 − state observed as a broad s-wave resonance, the existence of which had been questionable. Its possible effects on the determination of the astrophysical S-factor of 7Be( p , γ )8B at solar energy are discussed. The other state had not been observed in previous measurements, and its spin and parity were determined as 1 − .

25Al+p Elastic Scattering with CRIB

J. Pearson, A. A. Chen, S. Kubono, H. Yamaguchi, J. J. He, L. H. Khiem, A. Saito, G. Amadio, H. Fujikawa, M. Niikura, Y. Wakabayashi, T. Teranishi, S. Nishimura, Y. Togano, A. Odahara, f J. Y. Moon, Y. K. Kwon,, S. Cherubini, R. Pizzone, M. La Cognata, Department of Physics and Astronomy, McMaster University, Canada Centre for Nuclear Study, University of Tokyo, Japan Department of Physics, Kyushu University, Japan RIKEN, Japan Rikkyo University, Tokyo, Japan f Nishinippon Institute of Technology, Japan Department of Physics, Chung-Ang University, Korea University of Catania, Italy

Study of astrophysically important resonant states in

Department of Physics, Chung-Ang University, Republic of K orea aCenter for Nuclear Study, Graduate School of Science, Unive rsity of Tokyo, Japan bDepartment of Physics, Tohoku University, Japan cInstitute of Physics and Electronics, Vietnam dKEK (The High Energy Accelerator Organization), Japan eDepartment of Physics and Astronomy, McMaster University, Canada fDepartment of Physics, Yamagata University, Japan

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A new measurement of the proton resonance scattering on 7Be was performed up to the excitation energy of 6.8 MeV using the low‐energy RI beam facility CRIB (CNS Radioactive Ion Beam separator) at the Center for Nuclear Study (CNS) of the University of Tokyo. The excitation function of 8B above 3.5 MeV was successfully measured for the first time, providing important information about the reaction rate of 7Be(p,γ)8B, which is the key reaction in the solar 8B neutrino production. For more intensive experimental studies with RI beams, the development of a cryogenic gas target system is ongoing at CNS. In this paper a preliminary result of the 7Be experiment and the present status of the development of the target system are presented.

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A cryogenic gas target system was newly developed to produce intense RI beams at the low‐energy in‐flight radio‐isotope beam separator (CRIB) of the University of Tokyo. The main features of the cryogenic gas target system are the direct cooling of the target cell by a liquid N2 finger and the circulation of the target gas that goes through the liquid N2 tank. Hydrogen gas was cooled down to 85–90 K by liquid nitrogen and used as a secondary beam production target which has a thickness of 2.3 mg/cm2 at the gas pressure of 760 Torr. Intense RI beams, such as a 7Be beam of 2×108 particles per second, were successfully produced using the target.

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We have studied the proton resonance scattering of 7Be by using a pure 7Be beam produced at CRIB (CNS Radioactive Ion Beam separator; CNS stands for Center of Nuclear Study, University of Tokyo). The excitation function of 8B was measured up to the excitation energy of 6.8 MeV, with the thick‐target method. The excited states of 8B higher than 3.5 MeV were not known by the past experiments. This proton elastic scattering is also of importance in relation with the 7Be(p,γ)8B reaction, which is a key reaction in the standard solar model.

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The 7Be(p,γ)8B reaction is undoubtfully important to the understanding of the solar model. As a step in the direction of improving the accuracy of the S17 astrophysical factor, a study of the 7Be + p scattering was performed with the thick target method at the CRIB facility. In addition to its astrophysical significance, this reaction is also useful to clarify the nuclear structure of 8B. A primary beam of 7Li and a hydrogen gas target were used to produce a 7Be secondary beam at 7.69 MeV/u. This was the first time in which γ‐rays were measured in coincidence with protons, and we have successfully measured the inelastic contribution to the scattering cross section.