Analysis of the q q→ Z^* → hA →4τ process within the lepton-specific 2HDM at the LHC

We analyse light Higgs scalar and pseudoscalar associated hadro-production in the 2-Higgs Doublet Model (2HDM) Type-X (or lepton-specific) within the parameter space allowed by theoretical self-consistency requirements as well as the latest experimental constraints from the Large Hadron Collider (LHC), precision data and B physics. Over the viable regions of such a scenario, the Standard Model-like Higgs boson discovered at the LHC in 2012 is the heavier CP-even state H. Furthermore, in the Type-X scenario, due to large tanβ, the lighter Higgs scalar h and the pseudoscalar A mainly decay into two τ leptons. Therefore, we concentrate on analysing the signal process pp→ Z* → hA→ τ⁺τ⁻τ⁺τ⁻→ ν_ ν_ τₕ τₕ (where = e, μ whereas τₕ represents the hadronic decay of the τ) and explore the feasibility of conducting such a search at the LHC with a centre-of-mass energy of √s~= 14 TeV and a luminosity of L~=~300~fb⁻¹. To suppress the huge SM background, we confine ourselves to consider the fraction of signal events with two same-sign τ leptons further decaying into same-sign leptons while the other two τ leptons decay hadronically. We find that a combination of kinematical selection and machine learning (ML) analysis will yields significant sensitivity to this process at the end of the LHC Run 3.