Precision Timing of the ATLAS Level-1 Calorimeter Trigger: From Beam Splashes to High Luminosity Proton–Proton Collisions

The ATLAS Level-1 Calorimeter Trigger uses trigger tower signals from the ATLAS calorimeter as input. In real-time, it identifes high-pT objects, determines total and missing transverse energy sums and assigns bunch-crossing identification. Reliable operation requires collision signals to be synchronised at the nanosecond level. This timing was first established through the analysis of beam splash events and subsequently refined with data from LHC proton–proton collisions. In this contribution, details of the timing synchronization method as well as selected results from the timing adjustments are presented.