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

We present lattice QCD calculations of nucleon electromagnetic form factors using pion masses $m_{\pi }=149$, 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 $m_{\pi }=149\mathrm{MeV}$ in a large spatial volume ($m_{\pi }{L}_s=4.2$) 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 $Q^2=0.5{\mathrm{GeV}}^2$.