We investigate the phenomenological impact of incorporating vector-like bottom (VLB) quarks into the Type-II Two-Higgs-Doublet Model (2HDM-II). This framework introduces novel beyond-Standard-Model (BSM) decay channels B → Hb, B → Ab , and B → H − t , which are typically ignored by LHC pair-production searches focused on Standard Model (SM) final states ( B → Zb, B → hb, B → Wt ). Our analysis reveals that these BSM pathways significantly weaken current VLB mass constraints. In the 2HDM-II alignment limit, the mass limit for a singlet B shifts from approximately 1.5 TeV down to 1.34 TeV. For ( T, B ) and ( B, Y ) doublet configurations, the mass limits relax further to approximately 0.98 TeV, driven by the dominance of B → Hb and B → Ab decays, which can reach combined branching ratios of nearly 100%.
Benbrik et al. (Sun,) studied this question.