Massive Data Processing for the ATLAS Combined Test Beam

In 2004, a full slice of the ATLAS detector was tested for 6 months in the H8 experimental area of the CERN SPS, in the so-called Combined Test Beam, with beams of muons, pions, electrons and photons in the range 1 to 350 GeV. Approximately 90 million events were collected, corresponding to a data volume of 4.5 TB. The importance of this exercise was two-fold: for the first time the whole ATLAS software suite was used on fully combined real data. Besides, a novel production infrastructure was employed for the reconstruction of the real data as well as for a massive production of simulated events. This paper is a report on distributed Combined Test Beam Monte Carlo production with and without grid tools. In 2004, Monte Carlo production was started on the CERN LSF batch system and later it was, for the first time, performed on the LCG, with the simulation of about 4 Million events. In 2005, a more light-weight and user friendly system was tested on NorduGrid for the quick production of 210'000 photon events and 680'000 pion, muon and electron events. New Monte Carlo productions are already planed for the year 2006, using the new ATLAS production system