LHC-ATLAS Phase-I upgrade: calibration and simulation of a new trigger readout system for the Liquid Argon calorimeter

The ATLAS experiment at CERN's Large Hadron Collider is in the middle of the Phase-I upgrade for Run 3 (2021-2023) and the High-Luminosity LHC (2026-) where the instantaneous luminosities are going to be much higher than previously reached. In order to achieve a trigger rate compatible with the first stage trigger (100 kHz) without imposing higher energy thresholds, the ATLAS Liquid Argon Calorimeter group has been working on an upgrade of its trigger readout electronics. As part of this upgrade, new trigger Super Cells will be introduced, increasing the granularity of the trigger readout by a factor of ten with respect to Run 2. While the production and installation of the new electronics is underway, a calibration framework for the energy and timing measurement of the Super Cell readout is also being developed. The framework is created by using data taken in calibration runs with a pulsing system to establish the Super Cell pulse shape and other parameters, i.e. pedestal level, equivalent transverse energy for one ADC bit, and coefficients of an optimal filtering algorithm for energy calculation. In July 2019 we obtained the calibrations for the first installed digitizer board in the calorimeter end-cap. The new hardware has been verified to meet the design specifications. We are also developing a new simulation of the calorimeter using the calibrated parameters obtained during the commissioning of the new trigger readout system. The simulation takes into consideration the long bipolar pulse shape for any number of interaction per bunch crossing. This accounts for highly realistic out-of-time pileup effect.