Production of direct photons and neutral mesons at large transverse momenta by $\pi^{-}$ and $p$ beams at 500-GeV/c

We present results from the initial run of Fermilab experiment E706. The data include incident [pi][sup [minus]] and [ital p] beams at 500 GeV/[ital c] on Be and Cu targets, and span the kinematic ranges of transverse momentum and rapidity of 3.5[le][ital p][sub [ital T]][le]10 GeV/[ital c] and [minus]0.7[le][ital y][sub c.m.][le]0.7, respectively. We have measured cross sections for [pi][sup 0] and direct-photon production, as well as the [eta]/[pi][sup 0] production ratio. From the data on Be and Cu, we have extracted the nuclear dependence of [pi][sup 0] production, parametrized as [ital A][sup [alpha]]. The cross sections are compared with next-to-leading-log QCD predictions for different choices of the QCD momentum scales and several sets of parton distribution functions.