Multiple preequilibrium emission in Feshbach-Kerman-Koonin analyses

We describe how multiple preequilibrium emission can be included in the Feshbach-Kerman-Koonin (FKK) theory. By analyzing ($p,xn$) and ($p,xp$) reactions on zirconium, at incident energies of 80 and 160 MeV, the importance of multiple preequilibrium emission can be clearly seen. This mechanism accounts for much of the emission spectra and its importance extends to relatively high emission energies. We show that multiple preequilibrium must be included in FKK analyses at these incident energies in order to simultaneously satisfy unitarity and account for inclusive nucleon emission spectra. The importance of multistep processes is reduced in comparison to analyses which omit multiple preequilibrium. Our calculated angular distributions account for measurements except at the highest backward angles, where we underpredict the data. We compare our results with other analyses at these energies.