The 750 GeV diphoton excess and its explanation in 2-Higgs Doublet Models with a real inert scalar multiplet

TL;DR

This paper proposes that the 750 GeV diphoton excess observed at the LHC can be explained by an enhanced decay of a heavy Higgs boson in a 2-Higgs Doublet Model extended with a real inert scalar multiplet, which boosts the diphoton signal via multi-charged particle loops.

Contribution

It introduces a novel extension of the 2-Higgs Doublet Model with a real inert scalar multiplet, significantly enhancing the diphoton decay rate of a 750 GeV Higgs boson to match experimental observations.

Findings

Enhanced diphoton decay branching ratio by up to 1000 times.

Achieved a cross section consistent with LHC data for 750 GeV Higgs.

Demonstrated the role of multi-charged inert particles in decay processes.

Abstract

We discuss a possible explanation of the recently observed diphoton excess at around 750 GeV as seen by the ATLAS and CMS experiments at the Large Hadron Collider. We calculate the cross section of the diphoton signature in 2-Higgs Doublet Models with the addition of a real isospin scalar multiplet without a vacuum expectation value, where a neutral component of such a representation can be a dark matter candidate. We find that the branching fraction of an additional CP-even Higgs boson $H$ from the doublet fields into the diphoton mode can be significantly enhanced, by up to a factor of $10^3$, with respect to the case of the simple 2-Higgs Doublet Model. Such a sizable enhancement is realized due to multi-charged inert particle loops entering the $H\to \gamma\gamma$ decay mode. Through this enhancement, we obtain a suitable cross section of the $gg\to H \to \gamma\gamma$ process to explain the data with the fixed mass of $H$ being 750 GeV.