A search for direct photon production in 200 and 300 GeV/c proton-beryllium interactions

A search has been made for direct photon production in pBe interactions at 200 and 300 GeV/c over the kinematic region 1.5 < P_⊥ < 4.0 GeV/c and -0.7 < X_F < 0 (90° < θ_cms < 160°). An excess of single photons above that which is predicted from the measured π⁰ and η⁰ production is observed. Theratio of γ/π⁰ production is calculated assuming that the excess arises from direct photon production. We find that this ratio averages 0.070 +/- 0.025 (including systematic errors) in this region of X_F and P_⊥ for our 200 and 300 GeV/c data. We have used our measured value of the η/π⁰ ratio of 0.47 +/- 0.10 in the determination of the γ/π⁰ ratio. The variation of γ/π⁰ with X_F, P_⊥, X_R and θ_cms presented.

Present address: Brookhaven National Laboratory, Upton, NY 11973, USA.