Excited state systematics in extracting nucleon electromagnetic form   factors
  We present updated preliminary results for the nucleon electromagnetic form factors for non-perturbatively $\mathcal{O}(a)$ improved Wilson fermions in $N_f=2$ QCD measured on the CLS ensembles. The use of the summed operator insertion method allows us to suppress the influence of excited states in our measurements. A study of the effect that excited state contaminations have on the $Q^2$ dependence of the extracted nucleon form factors may then be made through comparisons of the summation method to standard plateau fits, as well as to excited state fits. 
Stefano Capitani, Michele Della Morte, Georg von Hippel, Benjamin   J\"ager, Bastian Knippschild, Harvey B. Meyer, Thomas D....
hep-lat