In order to use the quark-parton model, i.e. PDF,  scattered quarks have to be (quasi-)free during the interaction.  However, in the region of low Mhad values,  there is a non-negligible contribution from the final state interaction between the scattered quark and the remnant of the proton.  In this case,  the factorization of hard and soft processes does not hold,  so that one cannot simulate the process using the quark-parton model.

Actually,  in the region of Mhad<5GeV,  there are significant contributions from the Delta resonance production,  light vector-meson production and some other diffractive processes,  which are included in the simulation of the quasi-elastic process using SOPHIA and the parameterizations of ALLM and Brasse et al.

Comments  to  Tetsuo ABE (
Last  updated  on  Oct. 5,  2001