The $\bar{K}NN$ system with chiral dynamics

TL;DR

This paper calculates the $ar{K}NN$ system using chiral dynamics and the Fixed Center approximation, revealing bound states with specific energies and widths consistent with other methods, highlighting key physical effects.

Contribution

It introduces a simplified approach to study the $ar{K}NN$ system with chiral dynamics, emphasizing the effects of cluster size reduction and the $ ext{ extpi} ext{ extSigma}N$ channel.

Findings

Identifies a $ar{K}NN$ bound state around 40 MeV below threshold.

Finds a second peak near 27 MeV with similar width.

Results align with other chiral-based methods.

Abstract

We have performed a calculation of the scattering amplitude for the three body system $\bar{K}NN$ assuming $\bar{K}$ scattering against a $NN$ cluster, using the Fixed Center approximation to the Faddeev equations. The $\bar{K}N$ amplitudes, which we take from chiral unitary dynamics, govern the reaction and we find a $\bar{K}NN$ amplitude that peaks around 40 MeV below the $\bar{K}NN$ threshold, with a width in $|T|^2$ of the order of 50 MeV for spin 0 and has another peak around 27 MeV with similar width for spin 1. The results are in line with those obtained using different methods but implementing chiral dynamics. The simplicity of the approach allows one to see the important ingredients responsible for the results. In particular we show the effects from the reduction of the size of the $NN$ cluster due to the interaction with the $\bar{K}$ and those from the explicit considiration of the $ \pi \Sigma N $ channel in the three body equations.