The structure of events with a high psub(T) π0 or single photon

Differences in the structure of events associated with a high psub(T) π0 or a single photon were observed at the CERN intersecting Storage Rings. On the trigger side, the average associated charged multiplicity is significantly lower for single photon events than that for π0 events, and the rapidity and azimuthal correlations between the trigger particle and an additional particle depend on the nature of the trigger particle for small Δy and Δphi. On the away side, only small difference are seen. This is consistent with the hypothesis that the π0's form a part of a trigger jet while the single photons are produced directly in constituent scattering processes