The Elusive Gluon

TL;DR

This paper explores how vector resonances in composite Higgs models influence LHC search strategies, highlighting the significance of heavy gluon decays to top partners and their impact on mass bounds.

Contribution

It identifies overlooked decay channels of heavy gluons to top partners, suggesting modifications to LHC search strategies for vector resonances in composite Higgs models.

Findings

Heavy gluon decays to top partners can evade current bounds.

Mass bounds on heavy gluons can be as high as 2 TeV.

Modified search strategies are needed for better detection.

Abstract

We study the phenomenology of vector resonances in the context of natural composite Higgs models. A mild hierarchy between the fermionic partners and the vector resonances can be expected in these models based on the following arguments. Both direct and indirect (electroweak and flavor precision) constraints on fermionic partners are milder than the ones on spin one resonances. Also the naturalness pressure coming from the top partners is stronger than that induced by the gauge partners. This observation implies that the search strategy for vector resonances at the LHC needs to be modified. In particular, we point out the importance of heavy gluon decays (or other vector resonances) to top partner pairs that were overlooked in previous experimental searches at the LHC. These searches focused on simplified benchmark models in which the only new particle beyond the Standard Model was the heavy gluon. It turns out that, when kinematically allowed, such heavy-heavy decays make the heavy gluon elusive, and the bounds on its mass can be up to 2 TeV milder than in the simpler models considered so far for the LHC14. We discuss the origin of this difference and prospects for dedicated searches.