Perturbative QCD at next to leading order - A case for fracture functions

This talk provides a survey of the more recent developments in semi-inclusive deep inelastic scattering (DIS) processes in high energy collisions from the stand point of perturbative QCD. We discuss the factorization approach and the energy scale dependence of the relevant functions involved in the description of these processes. The central role played by the so called fracture functions to guarantee the correct cancellation of singularities is discussed in detail. We include recent results up to next to leading order with comments on the technical details involved in the calculation.