Study of jetlike structure in high-transverse-energy events produced inppcollisions at 400 GeV/c

The properties of events produced with high values of transverse energy in 400-GeV/c $\mathrm{pp}$ collisions are presented. The events were collected using the large-acceptance Fermilab multiparticle spectrometer. The fraction of events that are planar when a full-azimuthal-acceptance trigger is used does not increase with transverse energy. However, when additional requirements are applied to the data such as restricting the azimuth or polar-angle acceptance, limiting the particle multiplicity, or requiring dominance of electromagnetic or hadronic energy within an event, the fraction of planar events increases with transverse energy. None of these requirements explicitly impose planar structure and we conclude that the data show an indication for the emergence of jetlike structure. The trend of the data is consistent with the predictions of a QCD model; it cannot be described by an extrapolation of uncorrelated low-$p_t$ phenomena.