Hamburg 2016 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 107: Trigger und DAQ IV

T 107.5: Vortrag

Donnerstag, 3. März 2016, 17:45–18:00, VMP11 HS

Timing Calibration and Performance of the ATLAS Level-1 Calorimeter Trigger — •Claire Antel — Universität Heidelberg, Heidelberg, DE

The level-1 calorimeter (L1Calo) trigger is part of the first, and fastest-working, stage of online event selection at the ATLAS experiment at CERN. The system is required to process analogue signals, so-called trigger towers, from the calorimeter and identify and count particle candidates as well as missing and total transverse energy above configurable energy thresholds. The final acceptance decision is subsequently made by the central trigger processor using the combined information sent by all level-1 systems. The entire process is limited to 2.5 microseconds. One of the many aspects of the commissioning and performance checks of the ATLAS calorimeter trigger to ensure correct functionality is the input timing of the trigger tower signals. Signals, once received by L1Calo, have undergone several delays - time-of-flight delays as well as cable delays - and are different for each trigger tower. It is essential to synchronise the system so that signals from the same collision arrive simultaneously and the correct bunch crossing can thus be identified. Further fine-tuning of the signal delay, of 1 nanosecond precision, ensures that pulses are digitised at the pulse peak for optimum energy resolution. The procedure for the timing commissioning and findings in performance for Run 2 of the LHC will be hereby presented.