Nucleon resonances in the $\pi^- p \to K^0 \Lambda$ reaction near threshold

TL;DR

This paper models the $ o K^0 \Lambda$ reaction near threshold using an effective Lagrangian approach, highlighting the importance of nucleon resonances and meson exchanges in explaining experimental cross sections.

Contribution

It introduces a comprehensive model including nucleon resonances and meson exchanges to accurately describe the reaction near threshold, improving understanding of the reaction mechanisms.

Findings

Nucleon resonances significantly improve data fit.

Resonances dominate below 1.76 GeV energy.

Meson exchanges contribute minor effects.

Abstract

We investigate the two-body reaction $\pi^- p \to K^{0} \Lambda$ within the effective Lagrangian approach and the isobar model. In addition to the "background" contributions from $t$-channel $K^*$ exchange, $u$-channel $\Sigma(1192)$ and $\Sigma^*(1385)$ exchanges, and $s$-channel nucleon pole terms, the contributions from the nucleon resonances $N^*(1535)$, $N^*(1650)$, and $N^*(1720)$ are investigated. It is shown that the inclusion of these nucleon resonances contributions leads to a good description of the experimental total and differential cross sections data at low energy region. The $s$-channel $N^*(1535)$, $N^*(1650)$, and $N^*(1720)$ resonances and the $t$-channel $K^*$ exchange give the dominant contributions below $W = 1.76$ GeV, while the $u$-channel $\Sigma(1192)$ and $\Sigma^*(1385)$ exchanges give the minor contributions.