Intrinsic transverse momentum in the π−p→γγX reaction at 280 GeV/c

Abstract The correlation between the two high transverse momentum ( p t 2.75 GeV/ c ) photons of the reaction π − p → γγ X is studied at the beam momentum of 280 GeV/ c . QCD calculations beyond leading logarithms are not sufficient to explain the width of the distributions and the effects due to intrinsic transverse momentum of the incident partons are discussed.