Double Neutral Higgs production in the Two-Higgs doublet model at the LHC

TL;DR

This work analyzes double neutral-Higgs production in the CP-conserving 2HDM at the LHC, focusing on $pp \to h^0 h^0$, $pp \to h^0 H^0$, and $pp \to H^0 H^0$ under both decoupling and general scenarios. The authors compute tree- and loop-induced production amplitudes, incorporating widths and summing over all quark loops, using FeynArts/FormCalc and LoopTools, while enforcing unitarity, vacuum stability, perturbativity, and experimental constraints. They find that, in large regions of parameter space, the gluon-fusion cross sections can be up to two orders of magnitude larger than the SM, notably for large $m_{12}^2$ and small $\tan\beta$, with pronounced enhancements when $m_{H^0} \approx 2 m_{h^0}$ or when $H^0 \to h^0 h^0$ is open; in the decoupling limit non-decoupling heavy-Higgs-loop effects can still boost the effective triple-Higgs coupling $\lambda_{hhh}^{eff}$. The study also analyzes Higgs decay patterns across the four Yukawa types, highlighting final states such as $2b\,2\gamma$, $2b\,\tau^+\tau^-$, and $2b\,\mu^+\mu^-$ as promising probes of Higgs self-interactions, and discusses the prospects for distinguishing 2HDM scenarios from the SM and MSSM via these multi-Higgs signals.

Abstract

In this work we study the production and decay of two CP-even Higgs bosons in the general CP-conserving two-Higgs doublet model at the LHC. We also study the limiting case of the decoupling scenario. For each Yukawa version of the model, we look for the region of the parameter space where a signal would be seen at the LHC. Taking into account theoretical and experimental constraints on the two Higgs doublet model parameters, we show that the cross section can be two orders of magnitude above the corresponding Standard Model cross section. We have also studied in detail the decay profile of the Higgs bosons and showed that interesting signatures may emerge for some particular values of the parameters. In some scenarios, specific triple Higgs could be measured.

Figures (11)

• Figure 1: Tree-level contribution to $b\bar{b} \rightarrow S_i S_j$
• Figure 2: Triangle and box contributions to $gg \rightarrow S_iS_j$, where $S=h^0,H^0$ and $F$ is a generic quark.
• Figure 3: $pp \to h^0 h^0$ in the decoupling limit. On the right we show the strength of the one-loop corrected $h^0h^0h^0$ coupling relative to SM, for several values of $m_{12}$. On the left plot we show the production cross section for $m_{h^0}=115$ GeV as a function of $M_{\Phi}$ for the same values of $m_{12}$ as well as the corresponding SM cross section.
• Figure 4: The allowed regions of the 2HDM where the $\sigma(gg \to h^0 h^0)$ is larger than the corresponding SM cross section (left) and the 2HDM triple coupling $h^0h^0h^0$ and $h^0h^0h^0$ normalized to SM couplings (right). We show $m_{12}$ as a function of $\tan \beta$ for $m_{h^0}= 115$ GeV, $m_{A^0}= 350$ GeV, $m_{H^\pm} = 300$ GeV, $m_{H^0} = 250 \, GeV$ and $\sin \alpha = - 0.9$.
• Figure 5: The allowed regions of the 2HDM where the $\sigma(gg \to h^0 h^0)$ is larger than the corresponding SM cross section. We have chosen $m_{h^0}= 115$ GeV, $m_{A^0}= 350$ GeV, $m_{H^\pm} = 300$ GeV and $\tan \beta =1$. In the left panel we show $m_{12}$ as a function of $m_{H^0}$ with $\sin \alpha = - 0.9$. In the right panel we plot $m_{12}$ as a function of $\sin \alpha$ for $m_{H^0} = 250 \, GeV$.