Soft neutron production in DIS: a window to the final state interactions

Recently E-665 reported the first measurement of soft (En≤10 MeV) neutron production in deep inelastic scattering (DIS) off nuclei. We report the first theoretical analysis of the data. We find that the observed cross section can be quantitatively explained as due to the final state interactions (FSI) of low energy nucleons (EN∼ 200–400 MeV) produced in the elementary μN interactions. We argue that the data indicate strong a suppression of the FSIʹs of fast partons (hadrons) in DIS at high energies, and that studies of the soft neutron production would provide a new sensitive probe of the dynamics of FSIʹs in DIS both at fixed target energies and at the HERA eA collider.