Effects of spatial size, lattice doubling and source operator on the hadron spectrum with dynamical staggered quarks

TL;DR

This study investigates how lattice size, doubling, and source operators affect the hadron spectrum in lattice QCD with dynamical staggered quarks, providing insights into flavor symmetry restoration and finite size effects.

Contribution

It extends previous lattice QCD spectrum studies by using larger lattices, improved statistics, and additional propagator sources, revealing effects on hadron masses and flavor symmetry.

Findings

Good evidence for flavor symmetry restoration in meson masses

No significant finite size effect on nucleon mass at higher quark mass

Challenges in achieving consistent nucleon mass results with different sources

Abstract

We have extended our previous study of the lattice QCD spectrum with 2 flavors of staggered dynamical quarks at $6/g^2=5.6$ and $am_q=0.025$ and 0.01 to larger lattices, with better statistics and with additional sources for the propagators. The additional sources allowed us to estimate the $\Delta$ mass and to measure the masses of all mesons whose operators are local in time. These mesons show good evidence for flavor symmetry restoration, except for the masses of the Goldstone and non-Goldstone pions. PCAC is observed in that $m_\pi^2 \propto m_q$, and $f_\pi$ is estimated. Use of undoubled lattices removes problems with the pion propagator found in our earlier work. Previously we found a large change in the nucleon mass at a quark mass of $am_q=0.01$ when we increased the spatial size from 12 to 16. No such effect is observed at the larger quark mass, $am_q=0.025$. Two kinds of wall source were used, and we have found difficulties in getting consistent results for the nucleon mass between the two sources.