Speaker
Description
This work presents the consolidated contributions of the Spanish Tier-1 and Tier-2 centers to the computing infrastructure of the ATLAS experiment at the LHC. As of September 2025, our focus spans the final phase of Run 3, the ongoing preparations for the Long Shutdown 3 (LS3), and the strategic planning for the High-Luminosity LHC (HL-LHC) era. Our GRID infrastructure is continuously being optimized, encompassing robust data storage, efficient processing capabilities, and active involvement in software development and advanced computing tasks for the experiment. The fundamental objective remains twofold: first, to consistently provide stable data processing services 24/7, maintaining a reliability exceeding 97% for the Tier-1 and 95% for the Tier-2s, under the stringent conditions required by the experiment. Second, we are fully engaged in addressing the complex computing challenges inherent to the final stages of Run 3 and the early preparatory phase of the LS3 (July 2026 - June 2030). Central to our efforts is an active commitment to research and development challenges, strategically preparing for the more intricate and demanding HL-LHC phase. Annually, we generate billions of simulated events for diverse physics processes, leveraging national High-Performance Computing resources, including MareNostrum as part of the Spanish Supercomputing Network. We extensively utilize Data Lakes, a versatile paradigm essential for storing the massive datasets crucial for the experiment's physics analyses. Our centers are integral to the core GRID infrastructure, providing the reliability necessary for housing critical data and offering first-line support to local ATLAS physicists. A key development is the implementation of the "Facility for Interactive Distributed Analysis" (FIDA). This innovative initiative significantly streamlines the data analysis workflow for physicists at Spanish centers (IFIC, UAM, and IFAE). FIDA orchestrates the distributed nature of initial analysis phases with subsequent interactive exploration of reduced data files. The ultimate goal is to accelerate the production of publishable physics results and contributions for workshops and conferences. The ATLAS Tier-1 and Tier-2 sites in Spain have provided, and will continue to provide, substantial contributions to computing research and development. These efforts include the continuous evaluation of various models aimed at enhancing computing performance, optimizing resource utilization, and expanding data storage capacity to meet the unprecedented demands of the forthcoming High-Luminosity LHC era.