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

点击翻译按钮获取中文摘要

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.