Performance and optimization of analog and digital filtering algorithms for the Phase-II upgrade of the Hadronic End-Cap Calorimeter

The Large Hadron Collider (LHC) will be upgraded in 2024-26 to increase its beam intensity by a factor of up to 7 from its original design value. To cope with increased interaction rates and radiation exposure at this new High Luminosity LHC (HL-LHC), upgrades to multiple ATLAS detector subsystems are planned to take place alongside those to the LHC's accelerator chain. In this context, a re-design of the Hadronic End-Cap (HEC) calorimeter's electronic readout chain is required in order to maintain its energy reconstruction performance at the HL-LHC. The HEC readout electronics was implemented in a simulation framework capable of testing different analog filters and more complex digital signal processing algorithms. The expected degradation in energy resolution in the HEC at HL-LHC was estimated and optimization studies of different parameters of the HEC readout chain were carried out. Results have been used to make preliminary design decisions for the upgrade of the calorimeter readout electronics. Studies show that further improvements in the performance of the HEC energy reconstruction will have to come from new digital filtering algorithms that can better mitigate the effects of an increased interaction rate.