The Standard Model (SM) has been remarkably successful, yet several key questions remain
open, including the nature of dark matter, the matter–antimatter asymmetry, and the origin of
neutrino masses. Many extensions of the SM predict additional heavy particles, such as neutral
scalars (𝐻, 𝑆), pseudoscalars (𝐴), and charged Higgs bosons (𝐻
±
, 𝐻
±±), as realised for example
in Two-Higgs-Doublet Models, Supersymmetry, or hidden-sector Higgs models. We summarise
ATLAS Run-2 searches for heavy resonances in these scenarios. Using 140 fb−1
of 𝑝 𝑝 collisions
at √
𝑠 = 13 TeV, we present representative results in four channels: (i) 𝐻
± → 𝑊±ℎ → ℓ𝜈𝑏𝑏¯,
(ii) 𝐻
± → 𝜏𝜈, (iii) exotic decays 𝑆 → 𝑍𝑑 𝑍𝑑 → 4ℓ, and (iv) model-independent dijet resonance
searches using weakly supervised anomaly detection. No significant excess is observed. Limits
are set in benchmark frameworks (2HDM, hMSSM/MSSM, HAHM) and on generic resonance
cross sections, with notable sensitivity gains driven by advanced machine-learning techniques.