Advances in Energy Estimation for the ATLAS Experiment's Tile Calorimeter at the LHC

This work explores performance improvements achieved by energy estimation methods typically used in high-energy calorimetry systems. The goal is to evaluate their operation in high-luminosity conditions, such as in the ATLAS experiment in the Large Hadron Collider (LHC). The high-luminosity conditions increase the number of signals produced at each collision in such a way that the electronics from the calorimeter systems acquire information from adjacent events, producing the signal pile-up effect which degrades the efficiency of the energy estimation methods. In this context, the Optimal Filter (OF2) technique, currently employed in the ATLAS hadronic calorimeter (TileCal), is evaluated. Unlike the current version of the OF2 used in TileCal, this work proposes the use of the signal pile-up information, through the noise covariance matrix, to compute the filter coefficients. The results show that the proposed improvement significantly increases the OF2 efficiency, especially for readout channels that are more sensitive to the signal pile-up effect.