Excited state contamination in nucleon structure calculations
  Among the sources of systematic error in nucleon structure calculations is contamination from unwanted excited states. In order to measure this systematic error, we vary the operator insertion time and source-sink separation independently. We compute observables for three source-sink separations between 0.93 fm and 1.39 fm using clover-improved Wilson fermions and pion masses as low as 150 MeV. We explore the use of a two-state model fit to subtract off the contribution from excited states. 
Jeremy Green, Stefan Krieg, John Negele, Andrew Pochinsky, Sergey   Syritsyn
hep-lat