ATLAS WLCG Data Challenge 2024 planning and implementation

¹ School of Physics and Astronomy, University of Manchester, Oxford Rd, Manchester, M139PL, UK
² Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Bˇrehová 7, Prague, 115 19, Czech Republic
³ European Organization for Nuclear Research (CERN), 1211 Genève 23, Switzerland
⁴ University of Michigan: Ann Arbor, MI, US
⁵ Brookhaven National Laboratory: Upton, NY, US

^* e-mail: Alessandra.Forti@cern.ch

Published online: 7 October 2025

Abstract

ATLAS is participating in the World LHC Computing Grid (WLCG) Data Challenges (DC), a bi-yearly program established in 2021 to prepare for the data rates of the High Luminosity Large Hadron Collider (HL-LHC). In each challenge, the transfer rates are increased to ensure readiness for the full rates by 2029. The goal of the 2024 Data Challenge (DC24) was to reach 25% of the HLLHC expected transfer rates, with each experiment deciding how to execute the challenge based on agreed general guidelines and common dates. The ATLAS challenge was designed to test the ATLAS distributed infrastructure across 66 sites and was carried out over 12 days, with increasing rates and more complex transfer topologies, putting significant strain on the system. It was also the first time the new OAuth 2.0 authorization system was tested at such a large scale. This paper will discuss the planning of the challenge, the tools used to execute it, the agreed-upon transfer rates for the connections, and finally, the achieved results and any unrealized goals, along with an analysis of the bottlenecks. We will then describe how the challenge itself was executed, the results obtained, and the lessons learned. Finally, we will look ahead to the next challenge, currently scheduled for the end of 2026 or early in 2027, with 50% of HL-LHC rates.