Analysis of the gg→ H→ hh→4τ process in the 2HDM lepton specific model at the LHC

We analyse the signature of a light Higgs boson pair in the 2-Higgs Doublet Model(2HDM) Type-X (or lepton specific) over the parameter spaces allowed by theoretical self-consistency requirements as well as the latest experimental constraints from the Large Hadron Collider (LHC), precision test data and B physics. Over the viable regions of the latter, wherein the Standard Model (SM)-like Higgs boson discovered at the LHC in 2012 is the heavier CP-even state of the 2HDM, H, it is found that the SM-like Higgs boson can decay into a pair of the lighter CP-even Higgs boson, h, via the process H→ hh with a Branching Ratio (BR) of 5%-10% or so, (with 2 m_h < m_H =125 GeV). Furthermore, in the Type-X scenario, the lighter Higgs bosons h can dominantly decay into two τ's due to a large tanβ. Therefore, the pair of lighter Higgs bosons can altogether decay into a 4 τ final state. In order to suppress the huge SM background events, we confine ourself to consider the fraction of signal events with two Same-Sign (SS) τ's further decaying into same sign leptons while the other two τ's decay hadronically. By using Monte Carlo (MC) and Machine Learning (ML) tools, we thus focus on the analysis of the signal process pp→ H→ hh→τ^+τ^-τ^+τ^-→ℓ v_ℓℓ v_ℓτ_h τ_h (where ℓ= e, μ and τ_h means a hadronic decay of the τ) and explore the feasibility of such a search at the LHC for a collision energy √(s)= 14 TeV and a luminosity 300 fb^-1