Excited nucleon spectrum from lattice QCD with maximum entropy method

TL;DR

This study uses lattice QCD and the maximum entropy method to analyze excited nucleon states, revealing finite volume effects and insights into the Roper resonance's mass and level ordering puzzle.

Contribution

It applies the maximum entropy method to lattice QCD data to investigate excited nucleon states and addresses finite volume effects on the Roper resonance.

Findings

Finite volume effects significantly impact the Roper resonance mass.

Correcting for finite volume effects reduces the Roper resonance mass.

Results contribute to understanding the level order puzzle in nucleon excitations.

Abstract

We study excited states of the nucleon in quenched lattice QCD with the spectral analysis using the maximum entropy method. Our simulations are performed on three lattice sizes $16^3\times 32$, $24^3\times 32$ and $32^3\times 32$, at $\beta=6.0$ to address the finite volume issue. We find a significant finite volume effect on the mass of the Roper resonance for light quark masses. After removing this systematic error, its mass becomes considerably reduced toward the direction to solve the level order puzzle between the Roper resonance $N'(1440)$ and the negative-parity nucleon $N^*(1535)$.