Simple estimates for Fermi jets

The phenomenon of Fermi jets is investigated in the approximation of two colliding potential wells filled with degenerate Fermi gases of nucleons. A model is formulated which largely bypasses the explicit treatment of the relative motion of the nuclei, assumed to be governed by the window friction mechanism. Formulae for the velocity distributions and differential cross sections for neutrons and protons jetting through either target or projectile are derived. The numerical results are investigated systematically over a wide range of nuclear reactions. It is shown that the net linear momentum carried away by Fermi jets accounts for only a rather minor fraction of the observed missing momentum in typical heavy-ion fusion reactions.