Isolated double prompt photon production at CDF

We present a measurement of the cross section for production of two isolated prompt photons in p bar p collisions at √s = 1.8 TeV. The cross section, measured as a function of transverse momentum (PT) of each photon, is roughly three times what full QCD calculations predict. Calculations that only include the Born and box diagrams, which are commonly used to estimate the prompt diphoton background to Higgs decay at future hadron colliders, are lower than our measurement by roughly ii factor of five. We also study variables sensitive to KT: the transverse momentum of initial state partons. The vector sum of the transverse momenta of both photons, KT = |rvec PT1 + rvec PT2|, is compared to previous measurements at lower collision energies, and we find a roughly logarithmic increase with √s. The measured mean value is < KT >= 5.1 ± 1.1 GeV at √s = 1.8 TeV