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Measurement of the Photoproduction Cross Section with a Leading Proton at HERA |
| Reference |
T. Wildschek, talk presented at ICHEP 2000, July 2000 |
| Document |
Conference paper
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| Contact |
Wulfrin Bartel |
| Abstract |
The total cross-section for the semi-inclusive photoproduction process with a leading proton in the final state has been measured at centre-of-mass energies between 91 and 231~GeV. The measured cross-sections refer to the kinematic range with transverse momenta of the scattered proton restricted to $p_T \leq 0.2 \gev$ and $0.66 \leq z \leq 0.90$, where $z = E_p'/E_p$ is the scattered proton energy normalized to the beam energy. That is a region, in which diffractive processes are suppressed relative to processes with pion and reggeon exchange. The cross-section is measured to be about $7.7 \mub$ per unit $z$. It is found to be independent of the photon-proton centre-of-mass energy and the scattered proton momentum. The measured cross-sections are compared with semi-inclusive deep inelastic scattering data with a leading proton in the final state, which is subject to the same kinematic restrictions as in the case of photoproduction. This allows to study the transition from finite photon virtuality $Q^2$ to $Q^2=0$ in a model in which the proton structure function at low $Q^2$ is split into a nonperturbative vector meson dominated contribution and a partonic contribution. The VDM contribution determined in the framework of this model in case of the semi-inclusive process is only $23\%$ of the amount found in the inclusive reaction. |
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