Jun 2 – 7, 2019
Carnegie Mellon University
America/New_York timezone

## $K^+ \Lambda$ Photo- and Electroproduction off Proton

Jun 7, 2019, 10:15 AM
30m
Rangos 2

Dalibor Skoupil

### Description

New models for photo- and electroproduction of kaons on the proton were constructed [1,2,3] utilizing new experimental data from LEPS, GRAAL, and particularly CLAS collaborations. Higher spin nucleon (spin-3/2 and spin-5/2) and hyperon (spin-3/2) resonances were included using the consistent formalism and were found to play an important role in the description of data. In these analyses, we paid close attention to model predictions of the cross section at small kaon angles which are vital for accurate calculations of the hypernucleus-production cross section.

In order to account for the unitarity corrections at the tree level, we have introduced energy-dependent widths of nucleon resonances, which affect the choice of hadron form factors and the values of their cutoff parameters extracted in the fitting procedure.

On the road to electroproduction, we have implemented a new shape of electromagnetic form factors [4]. We have found out that for a reliable description of $K^+\Lambda$ electroproduction at small $Q^2$ it is necessary to take into account also a longitudinal coupling of virtual photons to nucleon resonances.

For the investigation of kaon photoproduction off the proton target, we have exploited also the hybrid Regge-plus-resonance (RPR) model [3] which provides an acceptable description of data in and above the resonance region. A novel feature of our version of the RPR model consists in applying a different scheme for the gauge-invariance restoration [5], which results in a need for a contact current. We reveal that the choice of the gauge-invariance restoration method may play a significant role for cross-section predictions at forward angles where data are scarce.

The sets of chosen nucleon resonances in our recent models are mutually quite well consistent and they also greatly overlap with the set selected in the Ghent analysis [6].

[1] D. Skoupil, P. Bydžovský, Phys. Rev. C 93, 025204 (2016).

[2] D. Skoupil, P. Bydžovský, Phys. Rev. C 97, 025202 (2018).

[3] P. Bydžovský, D.~Skoupil, arXiv:1903.02292.

[4] E. L. Lomon, Phys. Rev. C 66, 045501 (2002).

[5] H. Haberzettl et al., Phys. Rev. C 92, 055503 (2015).

[6] L. De Cruz et al., Phys. Rev. Lett. 108, 182002 (2012).