Opposite-Parity Contaminations in Lattice Nucleon Form Factors

TL;DR

This paper introduces a formalism using the PEVA technique to accurately compute nucleon form factors at finite momentum, revealing significant systematic errors in previous methods and offering a way to eliminate them.

Contribution

The paper develops a formalism for calculating spin-1/2 baryon form factors with PEVA, reducing systematic errors from opposite-parity contamination.

Findings

PEVA yields different nucleon form factors than conventional methods.

Systematic errors in previous calculations are approximately 20%.

The formalism effectively removes opposite-parity contamination.

Abstract

The recently-introduced Parity Expanded Variational Analysis (PEVA) technique allows for the isolation of baryon eigenstates at finite momentum free from opposite-parity contamination. In this paper, we establish the formalism for computing form factors of spin-1/2 states using PEVA. Selecting the vector current, we compare the electromagnetic form factors of the ground state nucleon extracted via this technique to a conventional parity-projection approach. Our results show a statistically significant discrepancy between the PEVA and conventional analyses. This indicates that existing calculations of matrix elements of ground state baryons at finite momentum can be affected by systematic errors of ~20% at physical quark masses. The formalism introduced here provides an effective approach to removing these systematic errors.