Electromagnetic production of kaon near threshold

TL;DR

This study models kaon production near threshold using an isobar approach, highlighting the significance of certain resonances and vector mesons, and discusses challenges in extending the model to electroproduction.

Contribution

It introduces a combined Feynman diagram and multipole formalism model for kaon production near threshold, emphasizing the role of the Lambda resonance and vector mesons.

Findings

Both pseudoscalar and pseudovector models fit photoproduction data well.

The Lambda resonance S_{01}(1800) significantly improves model accuracy.

Extending the model to electroproduction requires special form factors or refitting all parameters.

Abstract

Kaon photo- and electroproduction off a proton near the production threshold are investigated by utilizing an isobar model. The background amplitude of the model is constructed from Feynman diagrams, whereas the resonance term is calculated by using the multipole formalism. It is found that both pseudoscalar and pseudovector models can nicely describe the available photoproduction data up to W = 50 MeV above the threshold. The Lambda resonance S_{01}(1800) is found to play an important role in improving the model. In the case of double polarization observables Ox and Oz our result corroborates the finding of Sandorfi et al. Due to the large contributions of the K* and K1 vector mesons, extending the model to the case of electroproduction is almost impossible unless either special form factors that strongly suppress their contributions are introduced or all hadronic coupling constants are refitted to both photo- and electroproduction databases, simultaneously. It is also concluded that investigation of the kaon electromagnetic form factor is not recommended near the threshold region.