Measurement of Prompt Photon Production in 1.8-TeV Proton - Antiproton Collisions

Abstract

The inclusive production cross section of prompt photons with transverse energies 27 < EtEt < 40 GeV and in pseudorapidity 1.32 < ηη < 2.22 has been measured in proton antiproton collisions at s√s = 1.8 TeV. Using the data recorded by the CDF detector during the 1988-1989 TEVATRON collider run, corresponding to an integrated lurminosity of 3.8 ± 0.1 pb-1 3995 prompt photon candidate events are selected in the endplug electromagnetic calorimeter. From differences in the longitudinal cascade shower profile between a single photon and multi-photons from π0π0 and ηη meson decays, the number of prompt photon events in the candidates is extracted to be 1972 ± 353.The differences in the shower shape are obtained by a GEANT3 based Monte Carlo detector simulation, which has been careful1y studied and found to wel1 reproduce the electromagnetic cascade of electrons at various energies as wel1 as incident angles. The inclusive production cross section has been obtained to be σσ = 1.44 ± 0.09(stat..) ± 0.27(syst.) nb. The measurement agrees with the next-to-leading order QCD calculation using recent parton distribution functions. The differential cross section with respect to pseudorapidity has also been measured and found to be in good agreement with the QCD calculation. The photon event fraction and its dependence on the photon isolation are studied. The isolation dependence of the photon event fraction shows a consistency with the QCD prediction. Future prospects of prompt photon measurernents in the endplug region for the new data, which has been col1ected during 1992 to 1995 correspondingto roughly 110 pb-1 are also discussed.