Top-philic Dark Matter in a Hybrid KSVZ axion framework

We explore a two-component dark matter scenario in an extended Kim-Shifman-Vainshtein-Zakharov (KSVZ) axion framework. This hybrid setup incorporates an extra $SU(2)_L$ complex singlet scalar whose lightest component plays the role of one of the dark matter, while the QCD axion of the KSVZ model acts as a second dark matter candidate. In this work, we focus on accentuating the role of vector-like quark that naturally emerges in the KSVZ extension on the dark matter and collider phenomenology. Here, we demonstrate that the presence of this colored particle can significantly affect the allowed dark matter parameter space of the scalar dark matter by opening up additional co-annihilation as well as the direct detection channels. Moreover, the interaction between the color particle with the top quark and scalar dark matter provides a unique topology to generate a boosted-top pair with considerable missing transverse momentum at the LHC. Using jet substructure variables and multivariate analysis, here we show that one can already exclude a vast region of parameter space with 139 $\text{fb}^{-1}$ integrated luminosity at 14 TeV LHC.