Analysis of the $q\bar{q}\to Z^{\ast }\to hA\to 4\tau$ 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 $pp\to Z^{\ast }\to hA\to {\tau }^{+}{\tau }^{-}{\tau }^{+}{\tau }^{-}\to \ell {\nu }_{\ell }\ell {\nu }_{\ell }{\tau }_h{\tau }_h$ (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 $L=300f{b}^{-1}$. 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.

Comments: 24 pages, 11 figures, 7 tables. arXiv admin note: substantial text overlap with arXiv:2401.07289