Nucleon form factors on a large volume lattice near the physical point in 2+1 flavor QCD

TL;DR

This study computes nucleon form factors near the physical pion mass using large-volume lattice QCD, providing insights into nucleon structure and testing fundamental symmetries.

Contribution

First large-volume lattice QCD calculation of nucleon form factors at near-physical pion mass with detailed analysis of axial and pseudoscalar form factors.

Findings

Determined nucleon electric radius and magnetic moment accurately.

Verified the generalized Goldberger-Treiman relation.

Provided data on axial-vector and pseudoscalar form factors.

Abstract

We present results for the isovector nucleon form factors measured on a $96^4$ lattice at almost the physical pion mass with a lattice spacing of 0.085 fm in 2+1 flavor QCD. The configurations are generated with the stout-smeared $O(a)$-improved Wilson quark action and the Iwasaki gauge action at $\beta$=1.82. The pion mass at the simulation point is about 146 MeV. A large spatial volume of $(8.1~{\rm fm})^3$ allows us to investigate the form factors in the small momentum transfer region. We determine the isovector electric radius and magnetic moment from nucleon electric ($G_E$) and magnetic ($G_M$) form factors as well as the axial-vector coupling $g_A$. We also report on the results of the axial-vector ($F_A$), induced pseudoscalar ($F_P$) and pseudoscalar ($G_P$) form factors in order to verify the axial Ward-Takahashi identity in terms of the nucleon matrix elements, which may be called the generalized Goldberger-Treiman relation.