ATLAS experiment trigger menu and operation during heavy-ion data taking

The ATLAS experiment relies on a multi-level trigger system to efficiently select the most interesting events from the large data volumes produced at the LHC. This talk presents an overview of the ATLAS trigger system and its role in supporting the HI physics program, spanning from the least active, ultra-peripheral events up to very busy ultra-central events. In addition, the talk will discuss the heavy-ion data-taking period from the trigger operations perspective, highlighting the operational challenges and strategies used to ensure stable and efficient data collection.

The talk will also highlight new triggering capabilities introduced in the past few years, such as the exploitation of Transition Radiation Tracker (TRT) information and the Zero Degree Calorimeter (ZDC) for improved event classification and enhanced selection of photon-induced as well as ultra-central collisions. Together, these developments have significantly strengthened ATLAS’s ability to deliver high-quality heavy-ion data.