Opposite parity fermion mixing and baryons $1/2^{\pm}$

TL;DR

This paper introduces a modified K-matrix approach incorporating opposite parity fermion mixing, which explains certain baryon resonance features and restores symmetry relations in pion-nucleon scattering data.

Contribution

It develops a novel K-matrix variant that accounts for OPF mixing, providing a better description of specific partial waves and symmetry restoration.

Findings

Negative energy poles appear in the K-matrix due to OPF mixing.

Restoration of MacDowell symmetry in partial wave analysis.

Joint analysis confirms the importance of OPF mixing effects.

Abstract

We develop a variant of $K$-matrix, which includes the effect of opposite parity fermions (OPF) mixing, and apply it for description of $\pi N$ partial waves $S_{11}$ and $P_{11}$. OPF-mixing leads to appearance of negative energy poles in $K$-matrix and restoration of MacDowell symmetry, relating two partial waves. Joint analysis of PWA results for $S_{11}$ and $P_{11}$ confirms significance of this effect.