ATLAS Trigger Operations Notification System

The Large Hadron Collider (LHC) collides protons at 40 MHz, producing about 80 terabytes of data per second, while only around 8 GB/s can be stored. To manage this, ATLAS uses a two-level trigger system: Level 1 (L1) and High-Level Trigger (HLT), that filters events in real time to retain only the most relevant ones for offline analysis. Monitoring the trigger system is therefore crucial. Key operational quantities such as trigger rates (number of accepted events per second), deadtime (fraction of time when triggers are not active), luminosity (collision rate per unit area), available HLT processing slots (computational resources for event selection), and stream (logical collection of events grouped together according to their trigger selections or physics content), directly influence data taking efficiency and physics performance. For instance, excessive deadtime lowers the live fraction of triggers used for physics analysis, while unexpected fluctuations in the trigger rate or bandwidth may indicate misconfiguration or detector issues. Real-time visibility of these quantities is therefore essential for the Trigger Operations team to ensure smooth and efficient data taking.