The $A(K^-_{stop},\pi^\pm\Sigma^\mp)A'$ reaction on p-shell nuclei

TL;DR

This study investigates the $K^-_{stop}A$ reaction on p-shell nuclei, analyzing emission rates and in-medium effects related to the $ar{K}N$ interaction and the $ ext{Lambda}(1405)$ resonance, using the FINUDA spectrometer.

Contribution

It provides new measurements of emission rates and ratios in p-shell nuclei, highlighting significant in-medium effects and the role of the $ ext{Lambda}(1405)$ in these reactions.

Findings

Large deviation of $ ext{pi}^- ext{Sigma}^+/ ext{pi}^+ ext{Sigma}^-$ ratio from hydrogen

Evidence of strong in-medium effects possibly linked to $ ext{Lambda}(1405)$

Analysis of momentum spectra and missing mass behavior

Abstract

This letter is concerned with the study of the $K^-_{stop}A\rightarrow \pi^\pm\Sigma^\mp A'$ reaction in p-shell nuclei, i.e., $^{6,7}Li$, $^9Be$, $^{13}C$ and $^{16}O$. The $\pi^\pm\Sigma^\mp / K^-_{stop}$ emission rates are reported as a function of $A$. These rates are discussed in comparison with previous findings. The ratio $\pi^-\Sigma^+/\pi^+\Sigma^-$ in p-shell nuclei is found to depart largely from that on hydrogen, which provides support for large in-medium effects possibly generated by the sub-threshold $\Lambda(1405)$. The continuum momentum spectra of prompt pions and free sigmas are also discussed as well as the $\pi^\pm\Sigma^\mp$ missing mass behavior and the link with the reaction mechanism. The apparatus used for the investigation is the FINUDA spectrometer operating at the DA$\Phi$NE $\phi$-factory (LNF-INFN, Italy).