Measurement of the Neutron F2 Structure Function via Spectator Tagging with CLAS

We report on the first measurement of the F-2 structure function of the neutron from the semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to less than or similar to 100 MeV/c and their angles to greater than or similar to 100 degrees relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The F-2(n) data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65 < Q(2) < 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 F-2(n)/F-2(p) at 0.2 less than or similar to x less than or similar to 0.8 with little uncertainty due to nuclear effects.