K^0 pi^0 Sigma^+ and K^*0 Sigma^+ photoproduction off the proton

TL;DR

This paper reports measurements of specific photoproduction reactions off the proton, providing cross sections and angular distributions that reveal production mechanisms and hyperon states, aligning with recent theoretical models.

Contribution

First detailed measurement of $ ext{K}^0 ext{pi}^0 ext{Sigma}^+$ and $ ext{K}^{*0} ext{Sigma}^+$ photoproduction cross sections and angular distributions near threshold energies.

Findings

Flat angular distribution near threshold suggests s-channel dominance.

Observation of $ ext{Sigma}^*(1385)$ and higher hyperon states.

Forward enhancement indicates t-channel exchange contribution.

Abstract

The exclusive reactions $\gamma p \to K^{*0} \Sigma^+(1189)$ and $\gamma p \to K^{0} \pi^{0}\Sigma^+(1189)$, leading to the p 4$\pi^{0}$ final state, have been measured with a tagged photon beam for incident energies from threshold up to 2.5 GeV. The experiment has been performed at the tagged photon facility of the ELSA accelerator (Bonn). The Crystal Barrel and TAPS detectors were combined to a photon detector system of almost 4$\pi$ geometrical acceptance. Differential and total cross sections are reported. At energies close to the threshold, a flat angular distribution has been observed for the reaction $\gamma p\to K^{0} \pi^{0}\Sigma^+$ suggesting dominant s-channel production. $\Sigma^*(1385)$ and higher lying hyperon states have been observed. An enhancement in the forward direction in the angular distributions of the reaction $\gamma p \to K^{*0}\Sigma^+$ indicates a $t$-channel exchange contribution to the reaction mechanism. The experimental data are in reasonable agreement with recent theoretical predictions.