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1997 Fiscal Year Final Research Report Summary

Theoretical study of multistep direct reaction mechanism in preequilibrium nuclear reaction processes

Research Project

Project/Area Number 07640416
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field 素粒子・核・宇宙線
Research InstitutionKYUSHU UNIVERSITY

Principal Investigator

WATANABE Yukinobu  Kyushu University, Interdisciplinary Graduate School of Engineering Sciences, Associate Professor, 大学院・総合理工学研究科, 助教授 (30210959)

Co-Investigator(Kenkyū-buntansha) KAWAI Mitsuji  Kyushu University, Emeritus Professor, 名誉教授
Project Period (FY) 1995 – 1997
KeywordsPreequilibrium nuclear reaction / Multistep direct reaction / Semi-classical distorted wave approximation / SCDW model / Intermediate energy / Proton-induced reaction / Wigner transform / Nuclear in-medium effect
Research Abstract

We have proposed a new semi-quantal model to describe the multistep direct (MSD) reaction processes in preequilibrium nuclear reactions, which is called the semi-classical distorted wave model : it is referred to as the SCDW model. The purpose of this work is to investigate the MSD mechanism in the preequilibrium particle emission of nucleon-induced reactions in the intermediate energy region.
First of all, we have developed a way of calculating the MSD cross sections with the Quasi-Random Number Monte Carlo method, and succeeded in the SCDW calculations for the leading three MSD steps. The code was applied to proton-induced reactions on medium-heavy nuclei (i.e., ^<58>Ni and ^<90>Zr) for incident energies of several tens of MeV to 200 MeV.The result showed good agreement with the experimental data without any adjustable parameters, except at very forward and backward angles. We found that the underestimation seen at large angles is due to the momentum distribution of target nucleons given by the local Femi-gas model. To improve this situation, we have developed a new approach in which the Wigner transform of one-body density matrix is incorporated in the SCDW model. The discrepancy was indicated to be removed by using more realistic single-particle wave functions in the harmonic oscillator or Woods-Saxson ponetial, instead of the local Fermi-gas model.
In addition, we have found that the SCDW model is applicable to analyzes of (p, nx) reactions by taking into account the Q value correctly. Moreover, the result of SCDW calculations with in-medium NN cross sections showed that the in-medium effect is not much apreciable in the MSD process for incident energies up to 200 MeV.Finally, we have attempted to extend the SCDW model so that the matrix elements of sffective interaction is directly calculated, and investigated the off-shell effect on the MSD cross sections. As a result, we have not found a strong off-shell effect in the MSD reaction process continuum.

  • Research Products

    (10 results)

All Other

All Publications (10 results)

  • [Publications] M.Kawai, et al.: "Semi-Classical Distorted Wave Model for Multi-step Direct Process in(p,p'x)and (p,nx)Reactions" acta physica slovaca(Proc.of Int.Symp.on Pre-Equilibrium Reactions). 45. 693-704 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Y.Watanabe: "Application of the Feshbach-Kerman-Koonin model to(p,p'reactions at low incident energies" acta physica slovaca(Proc.of Int.Symp.on Pre-Equilibrium Reactions). 45. 749-756 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 渡辺 幸信: "原子核反応の前平衡過程と光学ポテンシャル" 統一的中性子ポテンシャル研究専門委員会報告書「中性子ポテンシャルの現状」(日本原子力学会). 209-219 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 河合 光路: "前平衡多段階直接過程(MSD)に関するコメント" 統一的中性子ポテンシャル研究専門委員会報告書「中性子ポテンシャルの現状」(日本原子力学会). 220-228 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Y.Watanabe et al.: "Status of Semi-Classical Distorted Wave(SCDW)Model" Proc. of the Fourth Symp.On Simulation of Hadronic Many-body SysTem:JAERI-Conf. 97-007. 104-113 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] M.Kawai, et al.: ""Semi-Classical Distorted Wave Model for Multi-step Direct Process in (p, P'x) and (p, nx) Reactions"" acta physica slovaca. Vol.45. 693-704 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Y.Watanabe: ""Application of the Feshbach-Kerman-Koonin model to (p, p) reactions at low incident enargies"" acta physica slovaca. Vol.45. 749-756 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Y.Watanabe: ""Preequilibrium processes in nuclear reactions and optical potentials" (in Japanese)" Report of Research Committee on Neutron Optical Potentials (Atomic Energy Society of Japan). 209-219 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] M.Kawai: ""Comments on preequilibrium multistep direct (MSD) processes" (in Japanese)" Report of Research Committee on Neutron Optical Potentials (Atomic Energy Society of Japan). 220-228 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Y.Watanabe et al.: ""Status of Semi-Classical Distorted Wave (SCDW) Model"" Proc.of the Fourth Symp.On Simulation of Hadronic Many-body System : JAERI-Conf. 97-007. 104-113 (1997)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1999-03-16  

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