Probing Charged Higgs Bosons through H^± → W^± A Decay in the Type-I Two-Higgs Doublet Model

A light pseudoscalar lighter than the 125 GeV Higgs boson remains allowed within the type-I Two-Higgs Doublet Model (2HDM), consistent with current collider constraints, including Higgs signal strength measurements and direct searches for additional Higgs bosons. At the Large Hadron Collider (LHC), the light pseudoscalar A can be pair-produced through the undetected decay of the Standard Model-like Higgs boson, h₁₂₅ → AA, when this channel is kinematically accessible (i.e., mA < m_h₁₂₅/2). For the charged scalar H^±, once open, the bosonic decay channel H^± → W±(*) A naturally dominates over the fermionic H^± → τ^±ν and H^± → tb channels, while relaxing the existing H^± limits. As a result, we propose searching for the charged Higgs boson through H^± → W±(*) A in the 4b+2j+ν final state. This channel is particularly sensitive to moderate-to-large tanβ values and provides an excellent complementary probe to searches based on fermionic H^± decays at the LHC. Our collider analysis demonstrates that this channel can probe a substantial region of the type-I 2HDM parameter space at the high-luminosity LHC.