Nucleon structure from 2+1 flavor domain wall QCD at nearly physical pion mass

TL;DR

This paper reports on lattice QCD calculations of nucleon structure using (2+1)-flavor domain wall fermions at near-physical pion masses, revealing insights into the pion cloud and providing improved data on nucleon properties.

Contribution

It introduces new lattice ensembles with lighter pion masses and larger volumes, enabling more accurate nucleon structure studies with minimized chiral symmetry breaking.

Findings

Preliminary nucleon mass estimates around 1 GeV.

Evidence for pion cloud effects in nucleon form factors.

Successful generation of ensembles at near-physical pion masses.

Abstract

The RBC and UKQCD collaborations have been investigating hadron physics in numerical lattice quantum chromodynamics (QCD) with (2+1) flavors of dynamical domain wall fermions (DWF) quarks that preserves continuum-like chiral and flavor symmetries. The strange quark mass is adjusted to physical value via reweighting and degenerate up and down quark masses are set as light as possible. In a recent study of nucleon structure we found a strong dependence on pion mass and lattice spatial extent in isovector axialvector-current form factors. This is likely the first credible evidence for the pion cloud surrounding nucleon. Here we report the status of nucleon structure calculations with a new (2+1)-flavor dynamical DWF ensembles with much lighter pion mass of 180 and 250 MeV and a much larger lattice spatial exent of 4.6 fm. A combination of the Iwasaki and dislocation-suppressing-determinant-ratio (I+DSDR) gauge action and DWF fermion action allows us to generate these ensembles at cutoff of about 1.4 GeV while keeping the residual breaking of chiral symmetry sufficiently small. Nucleon source Gaussian smearing has been optimized. Preliminary nucleon mass estimates are 0.98 and 1.05 GeV.