The future probe of the light Higgs boson pair production

TL;DR

This paper investigates the potential to detect light Higgs boson pairs in a two Higgs doublet model at the LHC, focusing on the scenario where the lighter Higgs is below 125 GeV and exploring the discovery prospects in future high-luminosity runs.

Contribution

It identifies the viable parameter space for a light Higgs in 2HDM and simulates pair production signals to assess detectability at the LHC.

Findings

Future high-luminosity LHC can detect the $b\bar{b}\gamma\gamma$ signal for certain parameter ranges.

The light Higgs scenario is consistent with current experimental constraints in the alignment limit.

The pair production rate is sensitive to the soft $\mathbb{Z}_2$ symmetry breaking parameter $m_{12}$.

Abstract

In this work we study the light Higgs scenario in the framework of two Higgs doublet model (2HDM). In this case the heavier CP-even Higgs boson $H$ in 2HDM is the SM-like Higgs with 125 GeV mass and a CP-even Higgs boson $h$ lighter than 125 GeV exhibits in the spectrum. We find that this scenario exists in the alignment limit of $\sin(\beta-\alpha)\simeq 0$ and is still allowed by the global fit of the 125 GeV Higgs and the direct searches for $H\to hh$ and $h\to \gamma\gamma$. The case of $M_h<M_H/2$ is highly constrained as the exotic decay mode $H\to hh$ is kinematically allowed. We focus on the $M_h>M_H/2$ case and simulate the pair production of the light Higgs boson at the LHC. The pair production is sensitive to the soft $\mathbb{Z}_2$ symmetry breaking term $m_{12}$ in the 2HDM potential through the Higgs self-couplings. We find that the future high-luminosity LHC can discover the $b\bar{b}\gamma\gamma$ signal in the region of $\tan\beta\lesssim 1$ and $0<m_{12}<100$ GeV allowed by the theoretical constraints.