EFFECTS OF JET AZIMUTHAL ANGULAR-DISTRIBUTIONS ON DIJET PRODUCTION CROSS-SECTIONS IN DIS

A Monte Carlo study of the azimuthal angular distribution around the v irtual boson-proton beam axis for dijet events in DIS at HERA is prese nted. In the presence of typical acceptance cuts on the jets in the la boratory frame, the azimuthal distribution is dominated by kinematic e ffects rather than the typical cos phi and cos2 phi dependence predict ed by the QCD matrix elements. This implies that the phi dependent par t of the QCD matrix elements contributes even to the dijet production cross section. Neglecting this phi dependence leads to an error of abo ut 5-8% in the production cross section for typical acceptance cuts in the laboratory frame. We also present first NLO results on the phi-de correlation of the jets through NLO effects. (C) 1997 Elsevier Science B.V.