Invariant cross section at √s = 28 GeV for coplanar high PT clusters selected by a hardware trigger

In a 400 GeV/c fixed target experiment using a set of geometrical calorimeter triggers we have determined a cross section for pp collisions producing two high PT coplanar clusters. This cross section was determined without using jet-finding algorithms or appealing to QCD Monte Carlo calculations. Corrections to the data were made by studying hardware triggers designed for that purpose or using experimental data from e+e− colliders. The magnitude of the experimental cross section and the PT slope both agree reasonably well with theoretical QCD predictions for parton-parton scattering that combine non-scaling behavior with fits to recent data from ep, μp, and vp experiments.