Measurement of the neutron F2 structure function via spectator tagging   with CLAS
  We report on the first measurement of the F2 structure function of the neutron from semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to < 100 MeV and their angles to < 100 degrees relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The F2n data collected cover the nucleon resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65 < Q2 < 4.52 GeV2, with uncertainties from nuclear corrections estimated to be less than a few percent. These measurements provide the first determination of the neutron to proton structure function ratio F2n/F2p at 0.2 < x < 0.8 with little uncertainty due to nuclear effects. 
N. Baillie, S. Tkachenko, J. Zhang, P. Bosted, S. Bultmann, M. E.   Christy, H. Fenker, K. A. Griffioen, C. E. Keppel, S. E....
nucl-ex hep-ex