Nuclear transparency and effective kaon-nucleon cross section from the A(e, e'K+) reaction

TL;DR

This study measures how transparent different nuclei are to kaons using electron scattering, revealing that in-medium kaon-nucleon interactions are weaker than free interactions and vary with atomic number.

Contribution

The paper introduces a novel method to extract in-medium effective kaon-nucleon cross sections from electron scattering data across multiple nuclei.

Findings

Effective kaon-nucleon cross sections are smaller than free cross sections.

Nuclear transparency depends on atomic number with a specific parameterization.

In-medium interactions differ significantly from free scattering measurements.

Abstract

We have determined the transparency of the nuclear medium to kaons from $A(e,e^{'} K^{+})$ measurements on $^{12}$C, $^{63}$Cu, and $^{197}$Au targets. The measurements were performed at the Jefferson Laboratory and span a range in four-momentum-transfer squared Q$^2$=1.1 -- 3.0 GeV$^2$. The nuclear transparency was defined as the ratio of measured kaon electroproduction cross sections with respect to deuterium, ($\sigma^{A}/\sigma^{D}$). We further extracted the atomic number ($A$) dependence of the transparency as parametrized by $T= (A/2)^{\alpha-1}$ and, within a simple model assumption, the in-medium effective kaon-nucleon cross sections. The effective cross sections extracted from the electroproduction data are found to be smaller than the free cross sections determined from kaon-nucleon scattering experiments, and the parameter $\alpha$ was found to be significantly larger than those obtained from kaon-nucleus scattering. We have included similar comparisons between pion- and proton-nucleon effective cross sections as determined from electron scattering experiments, and pion-nucleus and proton-nucleus scattering data.