Observed Differences in Event Structures of High-p/sub T/ pi exp 0 and Single Photon Events Produced in Pp Collisions at the CERN ISR

摘要

The direct photon production in pp collisions for c.m. energies 31 less than or equal to 63 GeV and transverse momenta of up to 9 GeV/c were measured at the ISR by use of a segmented lead/liquid argon calorimeter. The observed gamma / pi exp 0 ratio was found to be a significantly larger than zero at 4 GeV/c in p/sub T/, increasing to 0.4 at 9 GeV/c. The average multiplicity on the trigger side for the single-photon events was found to be significantly lower than for pi exp 0 events. The correlations in delta y and delta phi between the trigger particle and an additional particle were found to differe mainly at small delta y and delta phi. 3 figures. (ERA citation 06:001494)