Determination of the angular and energy dependence of hard constituent scattering from $\pi^{0}$ pair events at the CERN Intersecting Storage Rings

During the course of a general study of high transverse momentum phenomena in pp collisions, data have been obtained in which two roughly back-to-back\pi^{0}s, each of high transverse momentum, were detected. The\pi^{0}s were detected in two arrays of lead- glass Cerenkov counters centered at 90 degrees on either side of the interaction region. The analysis presented is motivated by two experiential observations. The first is that a high-P/sub T/\pi/sup 0 / is usually produced as part of a collimated jet of particles. The second is that such a\pi^{0} typically carries 70% or more of the total jet momentum and is very closely aligned with the jet axis. These observations are naturally interpreted in a hard-scattering model where the jet is composed of the fragments of the scattered constituent. In this picture, the mass of the dipion system is a measure of the centre-of-mass energy of the two partons which undergo the hard-scattering, and the angle of the dipion axis corresponds closely to the direction of the scattered partons