A search for the dimuon decay of the Standard Model (SM) Higgs boson isperformed using data corresponding to an integrated luminosity of 139 fb$^{-1}$collected with the ATLAS detector in Run2 $pp$ collisions at $\sqrt{s}=13$ TeVat the Large Hadron Collider. The observed (expected) significance over thebackground-only hypothesis for a Higgs boson with a mass of 125.09 GeV is$2.0\,\sigma$ ($1.7\,\sigma$). The observed upper limit on the cross sectiontimes branching ratio for $pp \to H \to \mu\mu$ is 2.2 times the SM predictionat 95% confidence level, while the expected limit on a $H \to \mu\mu$ signalassuming the absence (presence) of a SM signal is $1.1$ ($2.0$). The best-fitvalue of the signal strength parameter, defined as the ratio of the observedsignal yield to the one expected in the SM, is $\mu = 1.2 \pm 0.6$.

A search for the dimuon decay of the Standard Model Higgs boson with the ATLAS detector

Capua M.;Mastroberardino A.;Meoni E.;