Probing the low mass pseudoscalar in flipped Two Higgs Doublet Model

The phenomenology of the flipped two-Higgs-doublet model (2HDM) is relativelyless explored so far, as compared to the other, commonly discussed, types. It isfound that this scenario, like several others, admits of a light neutral pseudoscalar $A$ in the mass range 20 - 60 GeV, consistently with all current experimentaldata and theoretical constraints. However, the fact that such a pseudoscalar decays overwhelmingly into a $b\bar{b}$ pair makes its identification at theLarge Hadron Collider (LHC) a challenging task. After identifying the regionof the flipped 2HDM parameter space yielding a light pseudoscalar, we identifya useful search channel in the process $pp \rightarrow A Z(Z^{*}) \rightarrow b\bar{b} \ell^+ \ell^-$. A cut-based analysis,followed by one based on Boosted Decision Trees, shows that the light-$A$ scenario in flipped 2HDM should be detectable with rather high statisticalsignificance at the high-luminosity LHC run, even after including systematicuncertainties. Furthermore, part of the parameter space, especiallyaround $m_A = 30 - 40$ GeV, is amenable to detection at the discovery levelwithin Run-2 itself. This dataset supports the above study.