Diiractive Hard Scattering 1 Diiractive Hard Scattering 3

Diiraction is an old subject which has received much interest in recent years due to the advent of diiractive hard scattering. We discuss some theoretical models and experimental results that have shown new striking eeects, e.g. rapidity gaps in jet and W production and in deep inelastic scattering. Many aspects can be described through the exchange of a pomeron with a parton content, but the pomeron concept is nevertheless problematic. New ideas, e.g. based on soft colour interactions, have been introduced to resolve these problems and provide a uniied description of diiractive and non-diiractive events. This is part of the general unsolved problem of non-perturbative QCD and connnement. Abstract: Diiraction is an old subject which has received much interest in recent years due to the advent of diiractive hard scattering. We discuss some theoretical models and experimental results that have shown new striking eeects, e.g. rapidity gaps in jet and W production and in deep inelastic scattering. Many aspects can be described through the exchange of a pomeron with a parton content, but the pomeron concept is nevertheless problematic. New ideas, e.g. based on soft colour interactions, have been introduced to resolve these problems and provide a uniied description of diiractive and non-diiractive events. This is part of the general unsolved problem of non-perturbative QCD and connnement.