1996 Fiscal Year Final Research Report Summary
Nucleon resonance in electromagnetic reaction at GeV region
| Project/Area Number |
07640405
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | Osaka University |
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Principal Investigator |
SATO Toru Osaka University, Department of Physics, Graduate School of Science, Associate Professor, 大学院・理学研究科, 助教授 (10135650)
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| Co-Investigator(Kenkyū-buntansha) |
WAKAMATSU Masashi Osaka University, Department of Physics, Graduate School of Science, Research As, 大学院・理学研究科, 助手 (40135653)
OHTSUBO Hisao Osaka University, Department of Physics, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (30029491)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Electron Scattering / Bavyon Resonance / Meson photoproduction / Delta Resonance |
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| Research Abstract |
We have studied the structure of uncleon resonance using the electromagnetic probe around GeV region. Nucleon resonances can be studied using meson-nucleon scattering and meson-photoproduction processes. These resonances stay in the meson-nucleon continuum. Therefore the theoretical analysis including the coupling of resonance to the continuum and also the non-resonant processes is essentially important to determine the resonance properties.
In this project we focus on the electromagnetic structure of DELTA<@D233@>D2. In order to have a consistent treatment of meson nucleon system in terms of hadronic degrees of freedom, we used a method of unitary transformation, which was developed to study meson exchange current in nuclei. Using the unitary transformation method, we constructed effective hamiltonian for pion-nucleon scattering and pion-photoproduction including non-resonant processes. This model was shown to give a good description of the pion-nucleon scattering around the DELTA regi
… More
on. We studied the recent polarization data of pion photoproduction by LEGS.This quantity is known to be sensitive to the E2/M1 ratio of DELTA electromagnetic decay. As a results, we found non-resonance processes play important role in the electromagnetic decay of delta. Our value of M1 amplitude was found to be consistent with the prediction of constituent quark model, while the previous analyzes using multipole amplitude reported about 50% larger value. The difference is due to the contribution of the non-resonant process, which was not clearly separated in those analyzes. Finally our result of E2/M1 ratio is E2/M1 = (0.0(]SY.+-。[)1.3) %. This new value of E2/M1 gives an important information on the structure of delta in particular D-wave component of delta.
Currently we are extending our project into the higher energy region including eta production. Around the threshold of eta production, N^<**> (1535) dominates the amplitude. Therefore we expect a new insight on the N^<**> structure from this project. Less
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