Azimuthal Distribution of Quark-Antiquark Jets in DIS Diffractive Dissociation

We investigate the azimuthal distribution of quark-antiquark jets in DIS diffractive dissociation with large transverse momentum. In this kinematical region the matrix element is expressed in terms of the gluon structure function. For the transverse part of the cross section we find a cos(2φ)-distribution with the maximum at φ = ±π/2, i.e. the jets prefer a direction perpendicular to the electron plane. This is in contrast to boson gluon fusion where the qq̄ jet cross section for transversely polarized bosons peaks at φ = 0 and φ = π. We discuss the origin of this striking difference and present numerical results relevant for the diffractive dissociation at HERA. 1.) The observation and analysis of diffractive events in deep inelastic electron proton scattering at HERA [1, 2, 3, 4] has attracted much attention recently. Particular interest has been given to the question whether this process is dominated by the same (soft) Pomeron which is observed in diffractive dissociation of hadron-hadron scattering, or by the hard Pomeron which is associated with the observed rise of F2 at small x. As far as the (inclusive) diffractive structure function is concerned, one expects to see a combination of both the soft and the hard Pomeron. As a method of separating the hard component it has recently been suggested to look for final states of the diffractive system which consist of jets with large transverse momenta. The simplest configuration is a two-jet final state of a quark-antiquark pair. The cross section for this process, together with a Supported by Bundesministerium für Forschung und Technologie, Bonn, Germany under Contract 05 6HH93P(5) and EEC Program ”Human Capital and Mobility” through Network ”Physics at High Energy Colliders” under Contract CHRX-CT93-0357 (DG12 COMA). Supported by the US Department of Energy, High Energy Physics Division, Contract W-31-109-ENG-38.