Observation of a resonance in the K$_s$p decay channel at a mass of 1765 MeV/c$^2$

TL;DR

This paper reports the discovery of a resonance in the K$_s$p decay channel at 1765 MeV/c$^2$, observed in high-energy hyperon-nucleus interactions, indicating a possible $ ext{Σ}^{*+}$ state with a significant production cross section.

Contribution

The study provides the first observation of a resonance at 1765 MeV/c$^2$ in the K$_s$p channel with detailed production characteristics in hyperon interactions.

Findings

Resonance observed at 1765 MeV/c$^2$ with width 108 MeV/c$^2$

Production cross section increases linearly with (1-x_F)

No peaks found in K$^-$p and Λπ spectra

Abstract

We report on the observation of a K$_s$p resonance signal at a mass of 1765$\pm$5 MeV/c$^2$, with intrinsic width $\Gamma = 108\pm 22$ MeV/c$^2$, produced inclusively in $\Sigma^-$-nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region $x_F>0.7$, in this region its production cross section rises approximately linearly with $(1-x_F)$, reaching $BR(X\to K_S p)\cdot d\sigma /dx_F = (5.2\pm 2.3) \mu b $ per nucleon at $x_F=0.8$. The hard \xf spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a $\Sigma^{*+}$ state. No corresponding peaks were observed in the $K^- p$ and $\Lambda \pi^{\pm}$ mass spectra.