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Study of deeply-bound pionic atoms

深度结合的π离子原子的研究

基本信息

批准号：
09440100
负责人：
HAYANO Ryugo
金额：
$ 8.38万
依托单位：
THE UNIVERSITY OF TOKYO
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09440100/
关键词：
Pion Exotic Atom Deeply-bound states Effective mass in nuclei Nuclear reaction Eta meson Omega meson GSI 中間子原子量子色力学(QCD)パイ(π)中間子エータ(η)中間子オメガ(ω)中間子原子核実験 GSI研究所重陽子

项目摘要

The purpose of the research is to study theoretically as well as experimentally the deeply-bound pionic atom states, in particular is and 2p states, and to obtain information on the effective pion mass in nuclei. We also developed a new method to study the in-medium masses of eta and omega mesons. The major achievements during the two years are as follows :1. In order to search for the is bound state of pionic atom, we carried out an experiment using the ^<206>Pb(d, ^3He) reaction. The wavefunction of the pionic is state bound to a heavy nucleus has a large overlap with the nucleus, hence suitable to study the behavior of pions in nuclei. However, no such states have been experimentally observed. Theoretical studies have suggested that it is possible to identify 2p as well as is states as clear peaks in the excitation-energy spectrum, if Pb2O6 is chosen as the target. We therefore carried out the expriment, and successfully observed the 2p and is peaks. When the detailed analysis, being carried out, is completed, we expect to determine the pion effective mass with a high precision.2. The success of the pionic atom experiment motivated us to study the feasibility of studying the behavior of other mesons, such as eta and omega, by using the recoilless (d, ^3He) reaction. We first estimated the meson-nucleus optical potential, and determined the binding energies and widths of mesons by solving the Klein-Gordon equation. In both cases, the potentials were strongly attractive, and the existence of bound states are predicted. We then used the Green function method and the Eikonal approximation to estimate the reaction cross sections. We found that the bound-state peaks can be observed, even after taking account of various background processes. An experimental proposal based on this study was submitted to GSI, and was approved as S214.

本研究的目的是从理论和实验两方面研究深束缚态，特别是深束缚态和深束缚态，并获得原子核中有效介子质量的信息。我们还开发了一种新的方法来研究中质量的埃塔和欧米茄介子。两年来取得的主要成果如下：为了寻找电子原子的束缚态，我们利用^<206>Pb（d, ^3He）反应进行了实验。与重核结合的介子的波函数与原子核有很大的重叠，因此适合于研究介子在原子核中的行为。然而，没有实验观察到这样的状态。理论研究表明，如果选择Pb2O6作为目标，可以在激发能谱中识别出2p及其状态的清晰峰。因此，我们进行了实验，并成功地观察到2p和它的峰值。当详细的分析完成后，我们期望能以较高的精度确定介子的有效质量。电子原子实验的成功促使我们研究利用无后坐力（d, ^3He）反应来研究其他介子（如eta和omega）行为的可行性。我们首先估算了介子-原子核的光势，并通过求解Klein-Gordon方程确定了介子的结合能和宽度。在这两种情况下，势都是强吸引的，并且预测了束缚态的存在。然后，我们使用格林函数法和Eikonal近似来估计反应截面。我们发现，即使在考虑了各种背景过程之后，也可以观察到束缚态峰。基于本研究的实验方案已提交GSI，并被批准为S214。