Excited states in nucleon structure calculations

TL;DR

This paper reviews the challenges posed by excited state contamination in lattice QCD calculations of nucleon structure, emphasizing the development of methods to mitigate these effects and improve the accuracy of ground state measurements.

Contribution

It provides a comprehensive review of methods to handle excited state contributions in nucleon structure lattice QCD calculations, highlighting recent progress and remaining challenges.

Findings

Excited state contamination significantly affects nucleon structure calculations.

Recent methods have improved the extraction of ground state matrix elements.

Excited state effects remain a major systematic uncertainty in lattice QCD.

Abstract

Excited state contributions represent a formidable challenge for hadron structure calculations in lattice QCD. For physical systems that exhibit an exponential signal-to-noise problem they often hinder the extraction of ground state matrix elements, introducing a major source of systematic error in lattice calculations of such quantities. The development of methods to treat the contribution of excited states and the current status of related lattice studies are reviewed with focus on nucleon structure calculations that are notoriously affected by excited state contamination.