Ústav technické a experimentální fyziky

The study of kaon-hyperon electromagnetic production provides us with crucial knowledge on the spectrum of baryon resonances, including the so-called missing resonances, and interactions in the hyperon-nucleon systems arising from QCD. The correct description of the elementary production leads to obtaining reliable predictions of the excitation spectra in electroproduction of hypernuclei. In this talk, I will introduce isobar and Regge-plus-resonance (RPR) models which we use and I will compare our results with experimental data.

 

We have constructed new isobar models for photo- and electroproduction of $K^+ \Lambda$ on the proton with higher spin nucleon (spin-3/2 and spin-5/2) and hyperon (spin-3/2) resonances, which were found to play an important role in the data description. In addition, we have implemented a new shape of electromagnetic form factors and a longitudinal coupling of virtual photons to nucleon resonances in order to be able to describe also the process of electroproduction.

 

For the investigation of $K^+ \Lambda$ photoproduction, we have used, besides the isobar model, also the RPR model. A novel feature of our RPR model consists in applying a different scheme for the gauge-invariance restoration, which results in a need for a contact current. We reveal that the choice of the gauge-invariance restoration method plays a significant role for cross-section predictions at forward angles where data are scarce. This RPR approach was utilized to study also the \bar{D}^0 meson photoproduction off the proton target.

 

Recently, we have used our models for studying the $K^+ \Sigma^-$ photoproduction channel. In order to avoid the issue of overfitting, we have upgraded the fitting procedure with a regularization method with help of which we could reach very economical results in terms of assumed parameters.