Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA

Phys.Lett.B384:388-400,1996 In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken $x$ and $Q^2$ in the range 3 \cdot 10^{-4} < \xbj < 6\cdot 10^{-3} and $10 < Q^2 <100$~GeV$^2$