We report the first Lattice QCD calculation using the almost physical pion mass mpi=149 MeV that agrees with experiment for four fundamental isovector observables characterizing the gross structure of the nucleon: the Dirac and Pauli radii, the magnetic moment, and the quark momentum fraction. The key to this success is the combination of using a nearly physical pion mass and excluding the contributions of excited states. An analogous calculation of the nucleon axial charge governing beta decay has inconsistencies indicating a source of bias at low pion masses not present for the other observables and yields a result that disagrees with experiment.
@article{arxiv.1209.1687,
title = {Nucleon Structure from Lattice QCD Using a Nearly Physical Pion Mass},
author = {J. R. Green and M. Engelhardt and S. Krieg and J. W. Negele and A. V. Pochinsky and S. N. Syritsyn},
journal= {arXiv preprint arXiv:1209.1687},
year = {2014}
}