Excited-State Effective Masses in Lattice QCD

TL;DR

This paper introduces a black-box method to extract multiple excited-state energies from lattice QCD correlation functions, extending the effective-mass approach to improve accuracy and applicability.

Contribution

It extends the effective-mass method to incorporate multiple correlation functions and produce estimates for multiple excited states in lattice QCD.

Findings

Successfully applied to nucleon data

Comparable or improved accuracy over existing methods

Demonstrates robustness without initial guess dependence

Abstract

We apply black-box methods, i.e. where the performance of the method does not depend upon initial guesses, to extract excited-state energies from Euclidean-time hadron correlation functions. In particular, we extend the widely used effective-mass method to incorporate multiple correlation functions and produce effective mass estimates for multiple excited states. In general, these excited-state effective masses will be determined by finding the roots of some polynomial. We demonstrate the method using sample lattice data to determine excited-state energies of the nucleon and compare the results to other energy-level finding techniques.