Collider Signatures of Type-X 2HDM + scalar singlet dark matter at HL-LHC

As the 125 GeV Higgs becomes disfavored as a portal to the dark sector, one
is motivated to look beyond the SM-Higgs sector, into extended scalar-mediated
portal mechanisms. In this work we consider one interesting possibility of such
extended scalar sector, namely Type X two Higgs doublet with a scalar singlet
dark matter. This model with the advantage of light pseudoscalars also provides
the explanation for the observed anomalous magnetic moment of muon. The dark
matter phenomenology of this model is unique from the other types of two Higgs
doublet models. Therefore, it is quite intriguing to look for signatures
specific to this model at the collider experiments. In this work we take up the
task of finding suitable final states and regions of parameters space that can
be probed at the high-luminosity runs of LHC. We go beyond our rectangular
cut-based approach and use Artificial Neural Network which shows remarkable
improvement in terms of signal significance.