TDAQ Operations in ATLAS

The trigger system is a crucial part of the ATLAS experiment since it is responsible for the selection of LHC proton-proton collision data in real time, reducing the rate by 4 orders of magnitude (from 40 MHz to 1 kHz) for permanent storage and physics analysis.

We have a two-level trigger system formed by a hardware-based Level-1 trigger and a software-based High Level Trigger. The Level-1 trigger uses coarse granularity information from the calorimeter and muon systems while the High Level Trigger can access full granularity and full detector information to run sophisticated offline-like algorithms to refine the selection.

The ATLAS trigger has undergone a major upgrade for Run 3 with brand-new systems and a redesigned software framework to increase the signal acceptance and access corners of phase space not explored before.

IFIC Valencia has made major contributions to the trigger and coordinated this area during the Run 3 startup. The group is currently involved in different trigger activities, such as trigger software validation, trigger menu and operation, and tau lepton trigger identification performance studies.