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

Σ-N相互作用的研究对于理解八重态重子的物理是必不可少的。然而，与A相反，核介质中反映Σ-N相互作用基本性质的Σ单粒子(s.p)势还没有建立，因为实验信息很少。即使它的符号最近还没有确定，在KEK用不同的核靶测量了对应于π形成的(Σ^-，K^+)谱，测量精度较高，使用1.2GeV/cπ^-。基于这些光谱，发现由他们的DWIA分析得出的势是强烈的排斥力，高达100 MeV。考虑到理解Σ-N相互作用对于描述整个八重态重子-重子相互作用的重要性，有必要对KEK实验进行独立的分析。在这项研究中，我发展了一种半经典方法，并将其应用于(π^-，K^+)包含谱。双微分截面的表达式由入射介子扭曲波函数、出射K介子扭曲波函数和每个碰撞点处未被探测到的超子扭曲波函数组成，其中经典局域动量守恒成立。将该模型应用于在KEK用28Si靶获得的(π~(-)，K~(++))内含谱，结果表明，在30-50 MeV数量级的排斥Σ核势下，谱的形状和大小是令人满意地重现的。这个大小反过来限制了Σ-N势模型，从而提高了我们对完整八重态重子之间相互作用的理解。该框架可以很容易地用于描述其他包含谱，如(K，π)，(π，η)，(γ，K)等。考虑多步骤贡献也是直截了当的。

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.