Using Grid for the Babar experiment

The BaBar experiment has been taking data since 1999. In 2001 the computing group started to evaluate the possibility to evolve toward a distributed computing model in a Grid environment. We built a prototype system, based on the European Data Grid (EDG), to submit full-scale analysis and Monte-Carlo simulation jobs. Computing Elements (CE), Storage Elements (SE) and Worker Nodes (WN) have been installed at SLAC and in various European sites. A BaBar Virtual Organization (VO) and a test Replica Catalogue (RC) are maintained in Manchester, and the experiment is using three EDG testbed Resource Brokers (RB) in the UK and in Italy. First analysis tests were performed under the assumption that a standard BaBar software release was available in the Grid target sites, using RC to register information about the executable and the produced Ntuples. Hundreds of analysis jobs accessing either Objectivity or Root data files ran on the Grid. We tested the Monte Carlo simulation production using a farm of the ENFN-Grid test-bed customized to install an Objectivity database and run BaBar simulation software. First simulation production tests were performed using standard JDL commands and the output files were written on the closest Storage Element. A package that can be officially distributed to Grid sites not specifically customized for BaBar has been prepared. We are studying the possibility to add a user friendly interface to access Grid services for BaBar.