In designing a kinematic fitter for Radphi, a decision must be made
regarding how to handle the unmeasured momentum of the nucleus in
the initial and final states. In the quasi-elastic region, to a good
approximation these two are the same. That is, the A-1 nucleons
interact weakly with the outgoing nucleon, so as to insure momentum
conservation but not to appreciably affect the final-state proton
momentum. In this limit the nuclear cross section factorizes into
a
![$\gamma,p$](img1.png)
cross section times a nuclear structure function which
measures the momentum distribution averaged over all occupied proton
levels in the nucleus. In setting up a kinematic fit of the measured
momenta in the final state, it is convenient to replace the nuclear
structure function with a delta function, equivalent to the replacement
of the nuclear target with hydrogen. The purpose of this study is to
investigate the size of the errors associated with this approximation
in the quasi-elastic regime, and to look for any bias it may introduce
to the fit results.