Forward jet production at HERA

Deep inelastic scattering (DIS) of electrons against protons offers unique possibilities to study the partonic structure of matter, especially since the hardness of the interaction can be varied by selecting the energy and virtuality of the exchanged photon. HERA has extended the available region in the Bjorken scaling variable, x(Bj), down to values of x(Bj) similar or equal to 10(-4), for values of the four momentum transfer squared, Q(2), larger than a few GeV2, where perturbative calculations in QCD are expected to be valid. At these low xBj values, a parton in the proton can induce a QCD cascade, consisting of several subsequent parton emissions, before eventually an interaction with the virtual photon takes place. Measurement of the forward jet production cross section at small x(Bj) is Of special interest for studies of parton dynamics, since jets emitted close to the proton direction lie well away in rapidity from the photon end of the evolution ladder [1,2].