PT Journal AU ATLAS Collaboration (Aad, Gea Aparisi Pozo, JA Bailey, AJ Cabrera Urban, S Cardillo, F Castillo, FL Castillo Gimenez, V Costa, MJ Escobar, C Estrada Pastor, O Ferrer, A Fiorini, L Fullana Torregrosa, E Fuster, J Garcia, C Garcia Navarro, JE Gonzalez de la Hoz, S Gonzalvo Rodriguez, GR Guerrero Rojas, JGR Higon-Rodriguez, E Lacasta, C Lozano Bahilo, JJ Madaffari, D Mamuzic, J Marti-Garcia, S Martinez Agullo, P Mitsou, VA Moreno Llacer, M Poveda, J Prades Ibañez, A Rodriguez Bosca, S Ruiz-Martinez, A Sabatini, P Salt, J Santra, A Sayago Galvan, I Soldevila, U Sanchez, J Torro Pastor, E Valero, A Valls Ferrer, JA Vos, M TI A search for the dimuon decay of the Standard Model Higgs boson with the ATLAS detector SO Physics Letters B JI Phys. Lett. B PY 2021 BP 135980 EP 24pp VL 812 DI 10.1016/j.physletb.2020.135980 LA English AB A search for the dimuon decay of the Standard Model (SM) Higgs boson is performed using data corresponding to an integrated luminosity of 139 fb(-1) collected with the ATLAS detector in Run 2 pp collisions at root s = 13 TeV at the Large Hadron Collider. The observed (expected) significance over the background-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 section times branching ratio for pp -> H -> μμis 2.2 times the SM prediction at 95% confidence level, while the expected limit on a H -> μμsignal assuming the absence (presence) of a SM signal is 1.1(2.0). The best-fit value of the signal strength parameter, defined as the ratio of the observed signal yield to the one expected in the SM, is μ= 1.2 +/- 0.6. ER