Monte Carlo simulation in a GRID environment for the COMPASS experiment

In HEP experiments, like COMPASS at CERN, the production of Monte Carlo simulations is an important step to investigate several aspects of the experimental apparatus, minimizing the instrumental errors due to target acceptance, geometry and the errors deriving from the analysis cuts. Such a study is particularly important for the measurement of spin observables, where the control of the instrumental asymmetries is needed and larger statistics is required to get small error bars. Producing such a large amount of data requires considerable computing power. A way to satisfy these requirements is the new GRID technology. Since the beginning of 2004 the first truly accessible GRID infrastructure, deployed by INFN, is available. I will report on the new tests and results obtained using the INFN GRID computing resources to simulate the $\Lambda$ polarization in the semi-inclusive DIS of muons on a deuterium target polarized both longitudinally and transversely. These results will be compared with the available experimental results from COMPASS.