Measurement of Elastic omega Photoproduction at HERA

Abstract

The reaction $γp \rightarrow ωp$ $(ω\rightarrow π^+π^-π^0$ and $π^0\rightarrowγγ)$ has been studied in $ep$ interactions using the ZEUS detector at photon-proton centre-of-mass energies between $70$ and $90 GeV$ and $|t| < 0.6 GeV^2$, where $t$ is the squared four momentum transferred at the proton vertex.The elastic \ome photoproduction cross section has been measured to be $σ_{γp\rightarrow ωp} = 1.21\pm 0.12\pm 0.23 μb$. The differential cross section $dσ_{γp\rightarrow ωp} /d|t|$ has an exponential shape $e^{-b |t|}$ with a slope $b = 10.0\pm 1.2\pm 1.3 GeV^{-2}$. The angular distributions of the decay pions are consistent with s-channel helicity conservation. When compared to low energy data, the features of $ω$ photoproduction as measured at HERA energies are in agreement with those of a soft diffractive process. Previous measurements of the $ρ^0$ and $ϕ$ photoproduction cross sections at HERA show a similar behaviour.