Diphotons from an Electroweak Triplet-Singlet

TL;DR

This paper explores how an electroweak triplet and singlet pseudoscalar mixing can explain the 750 GeV diphoton excess, predicting distinctive collider signatures and broad parameter space coverage.

Contribution

It introduces a model with triplet-singlet mixing that enhances diboson decay channels and predicts observable signals at the LHC, expanding beyond singlet-only scenarios.

Findings

Diphoton excess at 750 GeV can be explained by triplet-singlet mixing.

Charged triplet components produce Wγ resonance signals at the LHC.

Parameter space can be probed extensively with 300 fb$^{-1}$} data.

Abstract

The neutral component of a real pseudoscalar electroweak (EW) triplet can produce a diphoton excess at 750 GeV, if it is somewhat mixed with an EW singlet pseudoscalar. This triplet-singlet mixing allows for greater freedom in the diboson branching ratios than the singlet-only case, but it is still possible to probe the parameter space extensively with 300 fb$^{-1}$. The charged component of the triplet is pair-produced at the LHC, which results in a striking signal in the form of a pair of $W\gamma$ resonances with an irreducible rate of 0.27 fb. Other signatures include multiboson final states from cascade decays of the triplet-singlet neutral states. A large class of composite models feature both EW singlet and triplet pseudo-Nambu Goldstone bosons in their spectrum, with the diboson couplings generated by axial anomalies.