Measurement of the cross section for production of two isolated prompt photons in pp-bar collisions at sqrt s =1.8 TeV.

We present measurements from events with two isolated prompt photons in [ital [bar p]p] collisions at [radical][ital s] =1.8 TeV. The differential cross section, measured as a function of transverse momentum ([ital P][sub [ital T]]) of each photon, is about 3 times what next-to-leading-order QCD calculations predict. The cross section for photons with [ital P][sub [ital T]] in the range 10--19 GeV is 86[plus minus]27(stat)[sub [minus]23][sup +32](syst) pb. We also study the correlation between the two photons in both azimuthal angle and [ital P][sub [ital T]]. The magnitude of the vector sum of the transverse momenta of both photons, [ital K][sub [ital T]]=[vert bar][bold P][sub [ital T]1]+[bold P][sub [ital T]2][vert bar], has a mean value of [l angle][ital K][sub [ital T]][r angle]=5.1[plus minus]1.1 GeV.