A Study of High Transverse Momentum Direct Photon Production in Interactions of 500 GeV/c $\pi^{-}$ and Proton Beams on a Beryllium Target

Abstract

This thesis presents the measurement of inclusive direct photon production cross section for experiment E706* for the data accumulated during 1987-88 fixed target run at Fermilab.$^{\dagger}$ The experiment employed a large liquid argon sampling calorimeter for electromagnetic particle detection with an energy resolution of approximately 15% $\sqrt{E}$. The spectrometer was exposed to incident $\pi^-$ and proton beam interacting with Beryllium (Be) target. The spectrometer triggered on high transverse momentum ($P_{\tau}$) electromagnetic showers. The incident $\pi^-$ beam was employed to measure the inclusive direct photon production cross sections from Be target in the $P_{\tau}$ range 3.5 < $P_{\tau}$ < 10 GeV/c. The incident proton beam was used to measure the inclusive direct photon production cross-sections from Be target in the $P_{\tau}$ range 4 < $P_{\tau}$ < 8 GeV/c. The cross sections are presented as a function of $P_{\tau}$ averaged over the rapidity ranges - .7 < y < - .2, - .2 < y < .2, .2 < y < .7 and - .7 < y < .7, as well as a function of rapidity integrated over $P_{\tau}$ range of 4 to 8 GeV/c. The ratio of direct photon production to $\pi^0$ production ($\gamma/\pi^0$ ) is also presented. The $\gamma/\pi^0$ ratio for $\pi^-$ and proton beam on Beryllium target is compared to leading log Quantum Chromodynarnics ( QCD) predictions. The direct photon cross sections are compared to next to leading log QCD predictions. Results are also compared to previous experiments.