Study of Asymmetric Weak decay of Polarized Hypernuclei Produced by(K^-, pi^0)

本课题旨在通过观察极化超核非介子弱衰变的不对称角分布，研究奇异度变化的弱超子-核子相互作用。有（K^ +, K^+）和n（K^-,）反应产生极化超核。我们证明了n（K^-, pi）反应给超核^1带来了更大的极化，我们计划在这个项目的开始使用它。同时，在KEK建立了新的束流线和超导谱仪。他们用（π ^+, K^+）反应来研究超核，在实践中相当有效，尽管用n（K^-, π）反应在原则上仍然是好的。利用（pi^+, K^+）反应，在KEK质子同步加速器上提出了“极化LAMBDA^^5He超核的非对称非介子弱衰变研究”实验。它于1992年获得批准（PS-E278），并于1993年底顺利完成。该实验有望对奇异度变化的弱超子-核子相互作用提供新的信息。此外，由于数据的质量远远超过以往的研究，我们应该能够提供关于LAMBDA^^5He超核的产生、结构和弱衰变的新信息。我们将再花一年的时间从中提取结果。同时，我们进行了相关的物理研究，得到了以下结果。1)准自由过程中λ超子的极化（参考文献3,5）2)准自由λ超子产生和超核产生的分离（参考文献6）3)（pi^+, K^+）反应和非对称非介子衰变产生的超核极化（参考文献2,4,7）4)超子和核子弱相互作用和弱非介子衰变（参考文献8,9）5)核中强子和弱超子-核子相互作用（参考文献8）

The purpose of this research project is to study strangeness changing weak hyperon nucleon interaction by observing asymmetric angular distibution of the nonmesonic weak decay of polarized hypernuclei. There are(pi^+, K^+)and n(K^-, pi)reactions to produce polarized hypernuclei. We showed that the n(K^-, pi)reaction introduces larger polarization to hypernuclei^1 and we planned to use it in the beginning of this project.Meanwhile new beam line and superconducting spectrometer are constructed at KEK.They made the study of hypernuclei by using the(pi^+, K^+)reaction quite effective in practice, although the use of n(K^-, pi)reaction is still good in principle. We proposed an experiment "Study of asymmetric nonmesonic weak decay of polarized LAMBDA^^5He hypernuclei" to the KEK proton synchrotron which uses(pi^+, K^+)reaction. It was approved(PS-E278)in 1992 and successfully completed at the end of 1993.The experiment is expected to give new information on the strangeness changing weak hyperon nucleon interaction. Futhermore since quality of data exceeds far the previous study, we should be able to gives new information on production, structure and weak decay of LAMBDA^^5He hypernuclei. We will spend another year to extract results out of them. Meanwhile we were carring out study of related physics and following results were obtained.1) Polarization of LAMBDA hyperons in the quasifree process (ref.3,5)2) Separation of quasifree LAMBDA production and production of hypernuclei (ref.6)3) Polarization of hypernuclei produced by the (pi^+, K^+) reaction and asymmetry nonmesonic decay (ref.2,4,7)4) Hyperon and nucleon weak interaction and weak nonmesonic decay (ref.8,9)5) Strong and weak hyperon nucleon interaction in nuclei (ref.8)