Analysis of the $gg\to H\to hh\to 4\tau$ process in the 2HDM lepton specific model at the LHC

Abstract

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 $H\to hh$ with a Branching Ratio (BR) of $5\%-10\%$ or so, (with $2m_h<m_H=125$ GeV). Furthermore, in the Type-X scenario, the lighter Higgs bosons $h$ can dominantly decay into two $\tau$'s due to a large $\tan \beta$. Therefore, the pair of lighter Higgs bosons can altogether decay into a 4 $\tau$ 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) $\tau$'s further decaying into same sign leptons while the other two $\tau$'s decay hadronically. By using Monte Carlo (MC) and Machine Learning (ML) tools, we thus focus on the analysis of the signal process $pp\to H\to hh\to {\tau }^{+}{\tau }^{-}{\tau }^{+}{\tau }^{-}\to \ell v_{\ell }\ell v_{\ell }{\tau }_h{\tau }_h$ (where $\ell =e,\mu$ and ${\tau }_h$ means a hadronic decay of the $\tau$) and explore the feasibility of such a search at the LHC for a collision energy $\sqrt{s}=\text{14 TeV}$ and a luminosity $\text{300}{\text{fb}}^{-1}$

Comments: 19 pages, 7 figures, 7 tables. arXiv admin note: text overlap with arXiv:2305.05788