PT Journal AU ATLAS Collaboration (Aad, Gea Aparisi Pozo, JA Bailey, AJ Cabrera Urban, S Cardillo, F Castillo Gimenez, V Costa, MJ Didenko Escobar, C Estrada Pastor, O 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 Mamuzic, J Marti-Garcia, S Martinez Agullo, P Miralles Lopez, M Mitsou, VA Monsonis Romero, L Moreno Llacer, M Navarro-Gonzalez, J Poveda, J Prades Ibañez, A Ruiz-Martinez, A Sabatini, P Salt, J Sanchez Sebastian, V Sayago Galvan, I Soldevila, U Sanchez, J Torro Pastor, E Valero, A Valls Ferrer, JA Villaplana Perez, M Vos, M TI Search for Higgs boson decays into a pair of pseudoscalar particles in the bb μμfinal state with the ATLAS detector in pp collisions at root s=13 TeV SO Physical Review D JI Phys. Rev. D PY 2022 BP 012006 EP 29pp VL 105 IS 1 DI 10.1103/PhysRevD.105.012006 LA English AB This paper presents a search for decays of the Higgs boson with a mass of 125 GeV into a pair of new pseudoscalar particles, H -> aa, where one a-boson decays into a b-quark pair and the other into a muon pair. The search uses 139 fb(-1) of proton-proton collision data at a center-of-mass energy root s = 13 TeV recorded between 2015 and 2018 by the ATLAS experiment at the LHC. A narrow dimuon resonance is searched for in the invariant mass spectrum between 16 GeV and 62 GeV. The largest excess of events above the Standard Model backgrounds is observed at a dimuon invariant mass of 52 GeV and corresponds to a local (global) significance of 3.3 sigma (1.7 sigma). Upper limits at 95% confidence level are placed on the branching ratio of the Higgs boson to the bb μμfinal state, beta(H -> aa -> bb μmu), and are in the range 0.2-4.0 x 10(-4), depending on the signal mass hypothesis. ER