Enabling efficient access to ATLAS data for Latin American collaborators

The ATLAS Collaboration consists of 167 institutions, in 37 countries of 6 continents. Approximately 2000 physicists participate in this truly worldwide enterprise. In order to enable fair and speedy access to the data to all Collaboration members, a complex distributed computing infrastructure has been designed and is now in the last phases of commissioning. Main cornerstones of this infrastructure are the Distributed Data Management System (DDM), the Distributed Production System (ProdSys) and the Distributed Analysis System (Ganga/p Athena), supplemented by the Information System and the Monitoring and Accounting tools. ATLAS can make use of three Grid middle ware stacks, provided by the projects EGEE (world-wide), NorduGrid (in the Scandinavian and associated countries) and OSG (in the USA). Several Latin American institutions joined ATLAS during the last couple of years, therefore we had to develop a work model that enables full and efficient access to all ATLAS data for small communities of geographically separated physicists. This paper describes the ATLAS Data and Computing Models, with particular attention to the issues of accessing data and running distributed analysis applications on the Grid. (Author)