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 $ ext{Lambda}(1405)$ and testing model consistency against CLAS photoproduction data.

Contribution

It demonstrates multiple parameter sets fit hadronic data well and identifies which solutions are compatible with photoproduction measurements.

Findings

Confirmed the two-pole structure of $ ext{Lambda}(1405)$

Identified parameter sets consistent with CLAS data

Uncertainty in the broad pole position

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.