$t\bar{t}t\bar{t}$ signatures through the lens of color-octet scalars

TL;DR

This paper investigates whether color-octet scalars (sgluons) in supersymmetric models can explain the ATLAS four-top excess, analyzing current constraints and projecting future discovery potential at the HL-LHC.

Contribution

It provides a reinterpretation of LHC four-top searches in the context of sgluon models, identifying parameter regions compatible with the ATLAS excess and projecting future sensitivities.

Findings

Sgluons heavier than 800 GeV are constrained by jets + missing energy searches.

A scalar or pseudoscalar sgluon can fit the ATLAS excess under certain scenarios.

Pseudoscalar sgluons in minimal models are ruled out by current data.

Abstract

We reinterpret two recent LHC searches for events containing four top quarks ($t\bar{t}t\bar{t}$) in the context of supersymmetric models with Dirac gauginos and color-octet scalars (sgluons). We explore whether sgluon contributions to the four-top production cross section $\sigma(pp \to t\bar{t}t\bar{t})$ can accommodate an excess of four-top events recently reported by the ATLAS collaboration. We also study constraints on these models from an ATLAS search for new phenomena with jets and missing transverse energy ($E_{\text{T}}^{\text{miss}}$) sensitive to signals with four top quarks. We find that these two analyses provide complementary constraints, with the jets + $E_{\text{T}}^{\text{miss}}$ search exceeding the four-top cross section measurement in sensitivity for sgluons heavier than about 800 GeV. We ultimately find that either a scalar or a pseudoscalar sgluon can currently fit the ATLAS excess in a range of reasonable benchmark scenarios, though a pseudoscalar in minimal Dirac gaugino models is ruled out. We finally offer sensitivity projections for these analyses at the HL-LHC, mapping the $5\sigma$ discovery potential in sgluon parameter space and computing exclusion limits at 95% CL in scenarios where no excess is found.