Probing Exotic Triple Higgs Couplings at the LHC

TL;DR

This paper explores the potential to detect exotic Higgs bosons with large triple couplings at the LHC, focusing on pair production processes in an extended Higgs model, and assesses their observability at the HL-LHC.

Contribution

It demonstrates how existing di-Higgs search strategies can be adapted to probe exotic Higgs pair production in an almost inert two Higgs doublet model, highlighting the sensitivity to new scalar masses.

Findings

Potential to detect additional neutral scalars up to 290 GeV at HL-LHC.

Enhanced pair production of exotic Higgses can be observed in specific final states.

Current searches can be repurposed for exotic Higgs discovery.

Abstract

In extended Higgs sectors that exhibit alignment without decoupling, the additional scalars are allowed to have large couplings to the Standard Model Higgs. We show that current nonresonant di-Higgs searches can be straightforwardly adapted to look for additional Higgses in these scenarios, where pair production of non-SM Higgses can be enhanced. For concreteness, we study pair production of exotic Higgses in the context of an almost inert two Higgs doublet model, where alignment is explained through an approximate $\mathbb{Z}_2$ symmetry under which the additional scalars are odd. In this context, the smallness of the $\mathbb Z_2$ violating parameter suppresses single production of exotic Higgses, but it does not prevent a sizeable trilinear coupling $hHH$ between the SM Higgs ($h$) and the additional states ($H$). We study the process $pp\rightarrow h^* \rightarrow HH$ in the final states $b\bar b b \bar b$, $b\bar b\gamma\gamma$, and multi-leptons. We find that at the HL-LHC these modes could be sensitive to masses of the additional neutral scalars in the range $130\mbox{ GeV} \lesssim m_H \lesssim 290\mbox{ GeV}$.