Search for decays of the Higgs boson into a pair of pseudoscalar particles decaying into bb¯τ⁺τ⁻ using pp collisions at √s = 13 TeV with the ATLAS detector

This paper presents a search for exotic decays of the Higgs boson into a pair of new pseudoscalar particles, H→aa, where one pseudoscalar decays into a b-quark pair and the other decays into a τ-lepton pair, in the mass range 12≤ m_a ≤60 GeV. The analysis uses pp collision data at √s = 13 TeV collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 140 fb⁻¹. No significant excess above the Standard Model (SM) prediction is observed. Assuming the SM Higgs boson production cross-section, the search sets upper limits at 95% confidence level on the branching ratio of Higgs bosons decaying into bb¯τ⁺τ⁻, B(H→aa→bb¯τ⁺τ⁻), between 2.2% and 3.9% depending on the pseudoscalar mass.