Speaker
Description
This contribution presents the search for the dimuon decay of the Standard Model Higgs boson ($H\rightarrow\mu\mu$) in the vector boson associated production (VH) mode using 2022–2024 ATLAS Run 3 pp collision data at $\sqrt{s}=13.6$ TeV. The $H\rightarrow\mu\mu$ channel probes the Higgs coupling to second-generation fermions despite its small branching ratio and challenging signal-to-background ratio. Multivariate techniques, including Boosted Decision Trees (BDTs) implemented with XGBoost, are used for event categorisation and signal discrimination. The VH categories form part of a combined analysis with earlier run 2 ATLAS data, which led to evidence for $H\rightarrow\mu\mu$ with an observed (expected) significance of $3.42\sigma$ ($2.46\sigma$) at $m_H = 125.09$ GeV. This contribution will also discuss potential improvements targeting the forthcoming analysis using the full ATLAS Run 3 dataset.