Electromagnetic Form Factors of Excited Nucleons via Parity-Expanded Variational Analysis

TL;DR

This paper introduces the parity-expanded variational analysis (PEVA) technique in lattice QCD to accurately extract excited nucleon form factors at non-zero momentum, overcoming parity mixing issues in boosted baryons.

Contribution

The paper presents a novel PEVA method that improves the isolation of boosted baryon eigenstates for form factor calculations in lattice QCD.

Findings

First calculations of excited nucleon form factors using PEVA

Demonstrates improved state isolation over traditional methods

Shows potential for more accurate baryon structure studies

Abstract

Variational analysis techniques in lattice QCD are powerful tools that give access to the excited state spectrum of QCD. At zero momentum, these techniques are well established and can cleanly isolate energy eigenstates of either positive or negative parity. In order to compute the form factors of a single energy eigenstate, we must perform a variational analysis at non-zero momentum. When we do this with baryons, we run into issues with parity mixing, as boosted baryons are not eigenstates of parity. The parity-expanded variational analysis (PEVA) technique is a novel method for ensuring the successful and consistent isolation of boosted baryon eigenstates. This is achieved through a parity expansion of the operator basis used to construct the correlation matrix. World-first calculations of excited state nucleon form factors using this new technique are presented, showing the improvement over conventional methods.