Spectra of Strangeness Production Reactions and Baryon Excited States in Nuclear Medium

研究Σ-N相互作用对于理解八重子的物理性质是必不可少的。然而，与A相反，由于实验信息匮乏，反映Σ-N相互作用基本性质的核介质中Σ单粒子（s.p）势尚未建立。最近，在KEK用1.2 GeV/c π^-用不同的靶核测量了Σ形成对应的（π^-,K^+）光谱，精度较高。根据这些谱图，发现从他们的DWIA分析中推断出的势是强排斥的，最大可达100 MeV。考虑到理解Σ-N相互作用对于我们描述整个八元子重子-重子相互作用的重要性，有必要对KEK实验进行独立分析。在本研究中，我开发了DWIA方法的半经典方法，并将其应用于（π^-,K^+）包含谱。双微分截面的表达式由入射的介子畸变波函数、出射的介子畸变波函数和未检测到的超子畸变波函数组成，其中每个碰撞点的经典局部动量守恒是成立的。将该模型应用于KEK用28Si靶得到的（π^-,K^+）包含谱，结果表明，用30-50 MeV数量级的Σ-nucleus排斥势可以很好地再现谱的形状和大小。反过来，这个量级限制了Σ-N势模型，从而提高了我们对完整八重子之间相互作用的理解。本框架可以很容易地应用于描述其他包含谱，如（K,π），（π,η）， （γ，K）等。考虑多步骤贡献也很简单。

The study of the Σ-N interaction is essential to understanding the physics of octet baryons. However, in contrast to the A, the Σ single-particle (s.p) potential in nuclear media, which reflects basic properties of the Σ-N interaction, has not been established, because experimental information is scare. Even its sign has not been established Recently, (π^-,K^+) spectra corresponding to Σ formation were measured employing various nuclei targets at KEK with better precision, using 1.2 GeV/c π^-. Based on these spectra, it was found that the potential deduced from their DWIA analysis is strongly repulsive, as large as 100 MeV. Considering the importance of understanding the Σ-N interaction for our description of the whole octet baryon-baryon interactions, it is desirable to carry out an independent analysis of the KEK experiments. In this study, I develop a semiclassical method for the DWIA approach and apply it to (π^-,K^+) inclusive spectra. The expression of the double differential cross section consists of the incoming pion distorted wave function, the outgoing kaon distorted wave function and the undetected hyperon distorted wave function at each collision point, where conservation of the classical local momentum holds. The application of this model to the (π^-,K^+) inclusive spectrum obtained with 28Si targets at KEK has shown that the shape and magnitude of the spectrum is satisfactorily reproduced by a repulsive Σ-nucleus potential of the order of 30-50 MeV. This magnitude, in turn, constrains the Σ-N potential model and thereby improve our understanding of the interactions between complete octet baryons. The present framework can be easily applied to describe other inclusive spectra, such as (K,π),(π,η), (γ,K), and soon. It is also straightforward to consider multistep contributions.