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Zeitschrift für Physik C
ISSN: 0170-9739 (printed version)
ISSN: 1431-5858 (electronic version)
Abstract Volume 73 Issue 1 (1996) pp 73-84
Measurement of elastic $\omega$ photoproduction at HERA
ZEUS Collaboration
, M. Derrick et al.
Argonne National Laboratory, Argonne, IL 60439, USA
Received: 14 August 1996
Abstract. The reaction $\gamma p \rightarrow \omega p$ $(\omega \rightarrow \pi^+\pi^-\pi^0$ and $\pi^0\rightarrow\gamma\gamma)$ has been studied in $ep$ interactions using the ZEUS detector at photon-proton centre-of-mass energies between 70 and $90\, {\rm GeV}$ and $|t| < 0.6\, {\rm GeV}^2$, where $t$ is the squared four momentum transferred at the proton vertex. The elastic $\omega$ photoproduction cross section has been measured to be $\sigma_{\gamma p\rightarrow \omega p} = 1.21\pm 0.12\pm 0.23 \,\mu\mbox{b}$. The differential cross section $d\sigma_{\gamma p\rightarrow \omega p} /d|t|$ has an exponential shape $\mbox{e}^{-b |t|}$ with a slope $b = 10.0\pm 1.2\pm 1.3\, {\rm GeV}^{-2}$. The angular distributions of the decay pions are consistent with s-channel helicity conservation. When compared to low energy data, the features of $\omega$ photoproduction as measured at HERA energies are in agreement with those of a soft diffractive process. Previous measurements of the $\rho^0$ and $\phi$ photoproduction cross sections at HERA show a similar behaviour.
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