Constraints on the chiral unitary $\bar KN$ amplitude from ${\pi}{\Sigma}K^+$ photoproduction data

TL;DR

This paper investigates the antikaon-nucleon interaction using a chiral unitary approach, confirming the two-pole structure of the ${ m extLambda}(1405)$ and analyzing photoproduction data to constrain model parameters.

Contribution

It demonstrates that only a subset of hadronic solutions are compatible with photoproduction data, refining the understanding of the ${ m extLambda}(1405)$ structure.

Findings

Multiple parameter sets fit hadronic data equally well.

The ${ m extLambda}(1405)$ has a two-pole structure with uncertain broad pole location.

Only some solutions agree with CLAS photoproduction data.

Abstract

A chiral unitary approach for antikaon-nucleon scattering in on-shell factorization is studied. We find multiple sets of parameters for which the model describes all existing hadronic data similarly well. We confirm the two-pole structure of the ${\Lambda}(1405)$. The narrow ${\Lambda}(1405)$ pole appears at comparable positions in the complex energy plane, whereas the location of the broad pole suffers from a large uncertainty. In the second step, we use a simple model for photoproduction of $K^+{\pi}{\Sigma}$ off the proton and confront it with the experimental data from the CLAS collaboration. It is found that only a few of the hadronic solutions allow for a consistent description of the CLAS data within the assumed reaction mechanism.