Semi-inclusive Deep Inelastic Electron Scattering off the Deuteron and   the Neutron to Proton Structure Function Ratio
  The production of slow nucleons in semi-inclusive deep inelastic electron scattering off the deuteron is investigated in the region $x \gsim 0.3$. It is shown that within the spectator mechanism the semi-inclusive cross section exhibits a scaling property even at moderate values of $Q^2$ ($\sim$ few $(GeV/c)^2$) accessible at present facilities, like $CEBAF$. Such a scaling property can be used as a model-independent test of the dominance of the spectator mechanism itself and provides an interesting tool to investigate the neutron structure function. The possibility of extracting model-independent information on the neutron to proton structure function ratio from semi-inclusive experiments is illustrated. The application of the spectator scaling to semi-inclusive processes off complex nuclei is outlined. 
Silvano Simula (INFN - Sezione Sanita')