Nucleon electromagnetic form factors from lattice QCD using a nearly physical pion mass

Abstract

We present lattice QCD calculations of nucleon electromagnetic form factors using pion masses ${m}_{\ensuremath{\pi}}=149$, 202, and 254 MeV and an action with clover-improved Wilson quarks coupled to smeared gauge fields, as used by the Budapest-Marseille-Wuppertal Collaboration. Particular attention is given to the removal of the effects of excited-state contamination by calculations at three source-sink separations and the use of the summation and generalized pencil-of-function methods. The combination of a calculation at the nearly physical mass ${m}_{\ensuremath{\pi}}=149\text{ }\mathrm{MeV}$ in a large spatial volume (${m}_{\ensuremath{\pi}}{L}_{s}=4.2$) and the removal of excited-state effects yields agreement with experiment for the electric and magnetic form factors ${G}_{E}({Q}^{2})$ and ${G}_{M}({Q}^{2})$ up to ${Q}^{2}=0.5\text{ }\text{ }{\mathrm{GeV}}^{2}$.