ON HIGH P(T) DIRECT PHOTONS, MESONS AND PQCD

Predictions of perturbative QCD (pQCD) for inclusive production of dir ect photons and mesons at high p(T) are tested using new high-statisti cs measurements from Fermilab experiment E706. Inclusive cross section s are presented for 515 GeV/c pi(-) and 530 and 800 GeV/c proton beams incident on a Be target, and for the kinematic range 4< p(T) <10 GeV/ c and central rapidities. Current Next-to-Leading Log (NLL) QCD calcul ations fail to accommodate the data. for usual choices of scales. The data indicate the presence of a substantial effective k(T); a phenomen ological model of k(T) effects improves the agreement between the calc ulations and the cross section data.