Collider Tests of (Composite) Diphoton Resonances

TL;DR

This paper investigates the Large Hadron Collider's ability to detect new pseudoscalar diphoton resonances up to a few TeV, exploring minimal models with photon or top-mediated production mechanisms, and connecting to potential signals like the 750 GeV excess.

Contribution

It introduces a model-independent effective operator framework and minimal composite models focusing on topological sectors, linking diphoton signals to composite dynamics and electroweak symmetry breaking.

Findings

Coupling to the top can explain the wide resonance width.

Effective operators provide a versatile analysis framework.

Models predict signatures for future collider tests.

Abstract

We analyze the Large Hadron Collider sensitivity to new pseudoscalar resonances decaying into diphoton with masses up to scales of few TeVs. We focus on minimal scenarios where the production mechanisms involve either photon or top-mediated gluon fusion, partially motivated by the tantalizing excess around 750 GeV reported by ATLAS and CMS. The two scenarios lead respectively to a narrow and a wide resonance. We first provide a model-independent analysis via effective operators and then introduce minimal models of composite dynamics where the diphoton channel is characterized by their topological sector. The relevant state here is the pseudoscalar associated with the axial anomaly of the new composite dynamics. If the Standard Model top mass is generated via four-fermion operators the coupling of this state to the top remarkably explains the wide-width resonance reported by ATLAS. Beyond the excess, our analysis paves the way to test dynamical electroweak symmetry breaking via topological sectors.