Measurement of charged particle multiplicities associated with large transverse momentum photons in proton-proton collisions

Abstract

We have measured the behaviour or charged-particle multiplicities as a function of the transverse momentum of photons produced at 90° in proton-proton collisions. The data were obtained at the CERN Intersecting Storage Rings (ISR) at a centre-of-mass energy of 53 GeV and cover the transverse momentum range 0 < p ⊥ < 4.5 GeV/ c. The total associated charge multiplicity increases with p ⊥ and most of the increase is found in a very wide cone opposite the detected photons. Partial multiplicities in the direction of the photons vary only slightly with p ⊥. However, multiplicities at small angles with respect to the beams decrease sharply with increasing p ⊥.