Evidence for the dimuon decay of the Higgs boson in pp collisions with the ATLAS detector

A search for the dimuon decay of the Higgs boson is presented based on pp collision data recorded by ATLAS during Run 3 of the Large Hadron Collider, corresponding to an integrated luminosity of 165 fb$^{-1}$ at $\sqrt{s} = 13.6$ TeV. To enhance the sensitivity, the results are combined with those from Run 2. An excess of events over the background is observed with a significance of $3.4 σ$ ($2.5 σ$ expected). The best-fit signal strength is $μ= 1.4\pm0.4$. This result provides evidence for the $H \to μμ$ decay with ATLAS data and offers a direct probe of the Higgs-boson Yukawa coupling to second-generation fermions.