Photoproduction of $\Lambda$ and $\Sigma^0$ hyperons using linearly polarized photons

TL;DR

This paper reports new measurements of polarization observables in hyperon photoproduction reactions, providing critical data to constrain baryon resonance models and improve understanding of nucleon structure.

Contribution

It presents the first measurements of beam-recoil observables for the $ ightarrow K^+ ightarrow$ reaction, enhancing the dataset for baryon resonance analysis.

Findings

New polarization data constrains resonance models

Significant data in previously unexplored energy regions

Supports the resonance set used in Bonn-Gatchina fits

Abstract

Background: Measurements of polarization observables for the reactions $\vec{\gamma} p \rightarrow K^+ \Lambda$ and $\vec{\gamma} p \rightarrow K^+ \Sigma^0$ have been performed. This is part of a programme of measurements designed to study the spectrum of baryon resonances. Purpose: The accurate measurement of several polarization observables provides tight constraints for phenomenological fits. Beam-recoil observables for the $\vec{\gamma} p \rightarrow K^+ \Sigma^0$ reaction have not been reported before now. Method: The measurements were carried out using linearly polarized photon beams and the CLAS detector at the Thomas Jefferson National Accelerator Facility. The energy range of the results is 1.71\,GeV $<W<$ 2.19\,GeV, with an angular range $-0.75 < \cos\theta^{\star}_K < +0.85$. Results: The observables extracted for both reactions are beam asymmetry $\Sigma$, target asymmetry $T$, and the beam-recoil double polarization observables $O_x$ and $O_z$. Conclusions: Comparison with theoretical fits indicates that in the regions where no previous data existed, the new data contain significant new information, and strengthen the evidence for the set of resonances used in the latest Bonn-Gatchina fit.