The detector and collider upgrades for the HERA-II running at DESY have considerably increased the demand on computing resources for the ZEUS experiment. To meet the demand, ZEUS commissioned an automated Monte Carlo(MC) production capable of using Grid resources in November 2004. Since then, more than one billion events have been simulated and reconstructed on the Grid which corresponds to two thirds of the overall MC production in this period. Based on the experience gained in this successful and efficient production on the Grid, a system has been developed for also running analysis jobs on the Grid. It allows standard ZEUS executables to be submitted to the Grid without any changes and with similar commands as used for the batch analysis. With this approach, the users can easily switch to running their analyses on the Grid and benefit from the additional resources without any Grid middleware knowledge. We present the design and implementation of the Monte Carlo production and the analysis systems which are both based on the ZEUS Grid-toolkit. Furthermore, we report on the status of these systems and our experience with large scale production on the Grid.

ZEUS