Electromagnetic matrix elements for negative parity nucleons

TL;DR

This paper presents preliminary lattice QCD results on electromagnetic form factors of negative parity nucleons, revealing differences in quark-sector contributions to magnetic form factors between states.

Contribution

It provides novel lattice QCD calculations of electromagnetic form factors for negative parity nucleons, highlighting differences in quark-sector contributions.

Findings

Electric form factors are similar between states.

Significant differences in quark-sector contributions to magnetic form factors.

Results suggest different quark dynamics in these states.

Abstract

Here we present preliminary results for the evaluation of the electromagnetic form factors for the lowest-lying negative-parity, spin-$\frac{1}{2}$ nucleons, namely the $S_{11}(1535)$ and $S_{11}(1650)$, through the use of the variational method. We find that the characteristics of the electric form factor, $G_{E}$, are similar between these states, however significant differences are observed between the quark-sector contributions to the magnetic form factor, $G_{M}$. Within simple constituent quark models, these states are understood to be admixtures of $s=\frac{1}{2}$ and $s=\frac{3}{2}$ states coupled to orbital angular momentum $\ell = 1$. Our results reveal a qualitative difference in the manner in which the singly-represented quark sector contributes to these baryon magnetic form factors.