PHENOMENOLOGY OF FORWARD HADRONS IN DEEP-INELASTIC SCATTERING - FRACTURE FUNCTIONS AND ITS Q(2) EVOLUTION

We analyze recent data on the production of forward neutrons in deep i nelastic scattering at DESY HERA in the framework of a perturbative QC D description for semi-inclusive processes, which includes fracture fu nctions. Using a model estimate for the nonperturbative piece of the f ragmentation process, in fairly good agreement with the available data , we analyze the Q(2) dependence of the resulting fracture functions, which is driven by nonhomogeneous evolution equations. We also propose a measurement of the pion production cross section in the target frag mentation region as a new test of perturbative QCD, which in this case predicts also a different Q(2) evolution with respect to the one give n by the usual Altarelli-Parisi equations.