Explanation of the excesses in associated di-photon production at 152 GeV in 2HDM

TL;DR

The paper investigates excesses around 152 GeV in di-photon production observed in ATLAS data, proposing that these can be explained by new Higgs bosons in 2HDM models, with implications for particle physics beyond the Standard Model.

Contribution

It introduces a 2HDM-based explanation for the 152 GeV excesses, analyzing decay modes and branching ratios to match observed significance levels.

Findings

Excesses can be explained by Drell-Yan production of new Higgs bosons.

Decay modes to $ au u$ and $tb$ yield significances up to 4σ.

A 2HDM with specific branching ratios can account for the excesses.

Abstract

Statistically significant excesses exist at around 152 GeV in associated di-photon production ($\gamma\gamma+X$) in the sidebands of SM Higgs analyses of ATLAS (using the full run-2 dataset). They are most pronounced in the single-$\tau$, missing-transverse-energy, four-jet and $\geqslant1\ell+\!\geqslant1b$-jet channels ($\approx3\sigma$) and can be explained by the Drell-Yan production of new Higgs bosons, i.e. $pp\to W^*\to H^\pm H^0$. We first examine the excesses in a simplified model approach, considering that $H^\pm$ decays to $\tau\nu$, $WZ$ or $tb$. Both the $\tau\nu$ and $tb$ decay modes individually lead to a significance of $\lessapprox4\sigma$ while for $WZ$ one can obtain at most $3.5\sigma$. This is because the decays of $WZ$ lead to multiple leptons contributing to the two-lepton channel which does not show an excess at 152 GeV. Next, we consider two-Higgs-doublet models where the charged Higgs does not decay to $WZ$ at tree-level, finding a significance of $\gtrapprox4\sigma$ for a branching ratio of the new neutral Higgs to photons of $\approx$2%. Even though this branching fraction is quite sizable, it can be obtained in composite models or via the Lagrangian term $\lambda_6 H_1^\dagger H_1 H_2^\dagger H_1+{\rm h.c.}$ breaking the commonly imposed $Z_2$ symmetry.