CP-odd scalar with vector-like fermions at the LHC

Many theories beyond the standard model (BSM) contain CP-odd scalars ($A$) and new vector-like fermions ($psi_{VL}$). The couplings of the $A$ to two standard model gauge bosons (i.e. $AVV$ couplings) cannot occur from renormalizable operators in a CP-conserving sector, but can be induced at the quantum loop level. We compute the $AVV$ effective couplings at the 1-loop level induced by the SM fermions and vector-like fermions, present analytical expressions for them, and plot them numerically. Using the 8~TeV Large Hadron Collider (LHC) $gammagamma$, $tau^{+} tau^{-}$ and $t bar t$ channel data, we derive constraints on the effective couplings of the $A$ to standard model (SM) gauge bosons and fermions, present the gluon-fusion channel cross-sections at the 8~and~14~TeV LHC, and present the branching-ratio of the $A$ into SM fermion and gauge-boson pairs. We present our results first model-independently, and then also for some simple models containing $A$ and $psi_{VL}$ in the singlet and doublet representations of $SU(2)$. In the doublet case, we focus on the two-Higgs-doublet (2HDM) Type-II and Type-X models.