LHC diphotons from electroweakly pair-produced composite pseudoscalars

TL;DR

This paper proposes a model where composite pseudoscalars, formed from new heavy fermions, can explain the 750 GeV diphoton excess observed by ATLAS and CMS, predicting additional multi-photon and dilepton signals.

Contribution

The paper introduces a new composite pseudoscalar model that accounts for the diphoton excess and predicts associated signals and a dark matter candidate.

Findings

Explains the 750 GeV diphoton excess with composite pseudoscalars.

Predicts significant 4-photon and same-sign dilepton events.

Proposes a neutral baryon-like dark matter candidate.

Abstract

Motivated by excess diphoton events reported by ATLAS and CMS, we show that composite pseudoscalars, bound states of heavy fermions under a new confining gauge theory, can be pair-produced by Drell-Yan production if the constituent particles are electrically charged. The decays of these pion-like bound states into two photons can explain the observed events near 750 GeV. The model predicts that there should be significant numbers of 4-photon events from decays of the pseudoscalar pairs, as well as same-sign dilepton pairs at a somewhat lower invariant mass, or multijet signals, coming from decays of charge-2 pseudoscalars. These states and their decays are necessary for avoiding stable charged baryon-like relics in the new confining sector. A neutral baryon-like dark matter candidate of mass $\sim N_c\times 375$ GeV is a further prediction of the model, for SU($N_c$) confining gauge group.