Reprocessing D0 Data with SAMGrid

The DØ experiment studies proton-antiproton collisions at the Tevatron collider based at Fermilab. Reprocessing, managing and distributing the large amount of real data coming from the detector as well as generating sufficient Monte Carlo data are some of the challenges faced by the DØ collaboration. SAMGrid combines the SAM data handling system with the necessary job and information management allowing us to use the distributed computing resources in the various worldwide computing centers. This is one of the first large scale grid applications in High Energy Physics (in particular as we are using real data). After successful Monte Carlo production and a limited data reprocessing in the winter of 2003/04, the next milestone will be the reprocessing of the full current data set by this autumn/winter. It consists of ~500 TB of data, encompassing one billion events. 1. The DØ experiment The DØ experiment is a worldwide collaboration of about 600 physicists from over 20 participating countries. The detector was designed to study high energy collisions between protons and antiprotons delivered by the Tevatron collider, based at Fermilab (Chicago, USA). 1.1 Tevatron at Fermilab The Tevatron is the highest energy particle collider currently operational. A first successful data taking period from 1992 to 1996, Run I, lead the two collider experiments CDF and DØ to the top quark discovery. A second run of collision, Run II, started in March 2001. The Tevatron has been significantly upgraded to deliver luminosity up to L = 2. 10 32 cmˉ 2.sˉ1, with an energy at the center of mass √s = 1.96 TeV. In order to reach such high luminosities, the whole accelerator chain had been upgraded as well. The “Main Ring” from Run I has been replaced by the “Main Injector”, housed in a separate tunnel to allow simultaneous operation of the Tevatron and other experiments (fixed target). An antiproton recycler has been installed in the same tunnel, and will allow a further increase in the total luminosity delivered by the accelerator. The Fermilab accelerator system for Run II described in Figure 1.1, consists now of five stages of accelerators : a Cockcroft-Walton preaccelerator, a linear accelerator (Linac), one synchrotron (Booster), the “Main Injector” and the Tevatron. Two storage rings device, the Debuncher and the Accumulator, are used to select and accelerate antiprotons after their production in the Target Station.