Photoproduction of ϱ0 and ω on hydrogen at photon energies of 20 to 70 GeV

Abstract

We present results on photoproduction of ϱ 0 and ω in the reactions γp→ π + π −p and γp→ π + π − π 0p by tagged photons in the energy ranges 20 to 70 GeV and 20 to 45 GeV, respectively. The production of the ϱ 0 shows dominantly the characteristics of a diffractive process with respect to the E γ and t dependence of the cross section and the spin density matrix. The ϱ 0 photoproduction yields on average over the photon energy range a total cross section of σ( γp→ ϱ 0p) = 9.4±0.1 μb with an additional systematic error of ±1 μb, and average slope parameters of the t distribution d σ/d t≈exp(− b| t| + ct 2), of b=9.1±0.1 GeV −2 and c = 3.1 ±±0.2 GeV −4. The shape of the ϱ 0 peak in the π + π − invariant spectra shows a skewing similar to that observed at lower energies. The photoproduction of ω is also consistent with a diffractive process and has a cross section of σ( γp→ ωp) = 1.2± 0.1 μb with an additional systematic error of ±0.2 μb. The average slope parameters of the t distribution are b=8.3 ± 1.3 GeV −2 and c = 3.4±2.6 GeV −4.