Analysis of the q\bar q\to Z^* \to hA \to4τ process within the lepton-specific 2HDM at the LHC

Abstract

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 \tan\beta, the lighter Higgs scalar h and the pseudoscalar A mainly decay into two \tau leptons. Therefore, we concentrate on analysing the signal process pp\to Z^{*} \to hA\to \tau^{+}\tau^{-}\tau^{+}\tau^{-}\to \ell \nu_\ell \ell \nu_\ell \tau_h \tau_h (where \ell= e, \mu whereas \tau_h represents the hadronic decay of the \tau) and explore the feasibility of conducting such a search at the LHC with a centre-of-mass energy of \sqrt{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 \tau leptons further decaying into same-sign leptons while the other two \tau 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.

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ORCID for S. Moretti: orcid.org/0000-0002-8601-7246

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