Charged Higgs Boson Mass Bounds in 2HDM-II: Impact of Vector-Like Quarks

We explore the phenomenology of charged Higgs bosons ($H^{\pm }$) and Vector-Like Quarks (VLQs), specifically the top-like $T$, within the Two Higgs Doublet Model Type-II (2HDM-II). We consider both a singlet VLQ $(T)$ and a doublet $(TB)$ scenario, demonstrating that the presence of VLQs influences the scalar sector, particularly by alleviating the stringent mass constraints on $H^{\pm }$ imposed by $B$-physics observables such as $B\to X_s\gamma$. This relaxation arises from modifications in the couplings between $H^{\pm }$ and Standard Model (SM) quarks, with the magnitude of the effect differing between the singlet and doublet cases. We further analyse the constraints from the oblique parameters $S$ and $T$ on VLQ mixing angles.