IFAE-Barcelona Fermilab Authors Ray Culbertson (rlc@fnal.gov) Mario Martinez (mmp@fnal.gov) Shin Shan Yu (eikoyu@fnal.gov) Carolina Deluca (cdeluca@fnal.gov) CDF, FNAL, P.0. Box 500, M.S. 318 Batavia, Illinois 60510 USA

Measurement of the Inclusive Direct Photon Cross Section We present preliminary results on inclusive direct photon production in p-pbar collisions at √s = 1.96 TeV using data collected with the upgraded Collider Detector at Fermilab in Run II corresponding to an integrated luminosity of 451pb-1. Measurements are performed as a function of the photon transverse momentum for photons with pT > 30 GeV/c and |&eta|<1.0. Photons are required to be isolated in the calorimeter (isolation < 2 GeV). The measurements are corrected to the hadron level and compared to NLO pQCD predictions. The theoretical predictions are not corrected for non-pQCD contributions. Blessed Results Trigger efficiency curve Events are collected with a trigger logic that requires at least one isolated photon with pT above 25 GeV/c. The trigger efficiency, as determined using Z->ee data, is 100% in the kinematic range considered in the measurement (shown below). Signal and Background Separation Signal and background (dominated by pi0 decays) contributions are determined by-bin-bin from a fit to the calorimeter isolation distribution in the data, for which photon and background templates are extracted from MC samples. Details for two bins in pT are presented below. Photon Fraction The signal fraction varies between 70% and 100% as the photon pT increases. A conservative ~15% systematic uncertainty is included. The Cross Section Result Data are unfolded back to the hadron level and the measurement is compared to NLO pQCD predictions from JetPhox, where theoretical predictions are not corrected for non-pQCD contributions (underlying event). Data and theory agree within uncertainties.