Towards the continuum limit of nucleon form factors at the physical point using lattice QCD

TL;DR

This study uses large-scale lattice QCD simulations at physical quark masses to accurately compute nucleon axial charge and form factors, analyzing discretization effects towards the continuum limit.

Contribution

It provides the first detailed lattice QCD results for nucleon form factors at the physical point with large spatial volume and multiple lattice spacings, addressing discretization uncertainties.

Findings

Calculated the axial charge and RMS radii of the nucleon.

Analyzed discretization effects on form factors and axial charge.

Provided continuum limit estimates for nucleon structure observables.

Abstract

We present results for the axial charge and root-mean-square (RMS) radii of the nucleon obtained from 2+1 flavor lattice QCD at the physical point with a large spatial extent of about 10 fm. Our calculations are performed with the PACS10 gauge configurations generated by the PACS Collaboration with the six stout-smeared $O(a)$ improved Wilson-clover quark action and Iwasaki gauge action at $\beta$ = 1.82 and 2.00 corresponding to lattice spacings of 0.085 fm and 0.063 fm respectively. We first evaluate the value of $g_A/g_V$ , which is not renormalized in the continuum limit and thus ends up with the renormalized axial charge. Moreover, we also calculate the nucleon elastic form factors and determine three kinds of isovector RMS radii such as electric, magnetic and axial ones at the two lattice spacings. We finally discuss the discretization uncertainties on renormalized axial charge and isovector RMS radii towards the continuum limit.