In-Situ Calorimeter Calibration at the ATLAS Detector with $Z \rightarrow ee$ Events

This presentation will describe the in-situ calibration of the ATLAS electromagnetic calorimeter using $Z \rightarrow ee$ events. The method is based on constraining the invariant mass distribution of the two decay electrons to the known $Z$-boson line shape. Monte carlo results will be presented showing that this $Z \rightarrow ee$ calibration method can achieve a long-range calorimeter resolution term of 0.5\%, the value calculated as necessary to achieve the ATLAS experiment's physics goals (such as detection $H \rightarrow \gamma\gamma$). Performance and comparison of different methods to extract the calibration constants will be shown.