Search for a new pseudoscalar decaying into a pair of muons in events with a top-quark pair at √s=13 TeV with the ATLAS detector Aad, Georges Rodríguez Chala, Mikael Atlas Collaboration, / A search for a new pseudoscalar a-boson produced in events with a top-quark pair, where the a-boson decays into a pair of muons, is performed using √s=13  TeV pp collision data collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139  fb−1. The search targets the final state where only one top quark decays to an electron or muon, resulting in a signature with three leptons eμμ and μμμ. No significant excess of events above the Standard Model expectation is observed and upper limits are set on two signal models: pp→tta and pp→tt with t→H±b, H±→W±a, where a→μμ, in the mass ranges 15  GeV<ma<72  GeV and 120  GeV≤mH±≤160  GeV. 2024-05-03T06:45:05Z 2024-05-03T06:45:05Z 2023-11-28 journal article G. Aad et al. Search for a new pseudoscalar decaying into a pair of muons in events with a top-quark pair at √s=13 TeV with the ATLAS detector. Physical Review D. 108, 092007 (2023) [10.1103/PhysRevD.108.092007] https://hdl.handle.net/10481/91344 10.1103/PhysRevD.108.092007 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional American Physical Society