The Higgs boson mass is one of the most important free parameters in the Standard Model, and is crucial to determining the coupling strength to Standard Model particles. This is most precisely measured in the $H\rightarrow \gamma \gamma$ and $H\rightarrow ZZ^{*} \rightarrow 4\ell$ channels, for which the final states are fully reconstructable.
This report presents a measurement for the Higgs boson mass is extracted in the four-lepton decay channel using 139 $fb^{−1}$ of proton-proton collision data at the Large Hadron Collider by ATLAS, corresponding to the full Run 2 dataset For a Higgs boson with $m_{H}$ = 125 GeV, the expected total (stat) uncertainty is 181 MeV (178 MeV).