Siyuan Yan - HiggsHunting2022 - Talk

In this talk, I’ll present a measurement of the Higgs boson mass in the four-lepton decay channel using 139 fb−1 of proton-proton collision data at the Large Hadron Collider recorded by the ATLAS detector, corresponding to the full Run 2 dataset. I’ll highlight the main improvements in this analysis, including the updated muon momentum systematics, use of quantile-regression neural network, and signal and background models. These have led to 10% reduction in the combined uncertainty, with 40% reduction in the systematic uncertainty with respect to the previous Higgs to four-lepton mass measurement by the ATLAS detector. The observed Higgs boson mass is at 124.99 GeV with the observed total (stat) uncertainty of 0.19 GeV (0.18 GeV).