Four tops and the t tbar forward-backward asymmetry

TL;DR

This paper investigates how a hypothetical colour octet vector could explain the Tevatron's top quark asymmetry and predicts observable four-top production signals at the LHC, with cross sections sensitive to the octet's mass and couplings.

Contribution

It provides a detailed calculation of four-top production cross sections in models with a massive colour octet vector, exploring the parameter space consistent with current experimental limits.

Findings

Masses above 650 GeV are allowed and can be probed with existing LHC data.

Four-top cross section increases significantly at higher LHC energies, enhancing detection prospects.

Current LHC data already constrains some parameter regions of the model.

Abstract

New colour octet vectors below the TeV scale could explain the anomalous t tbar forward-backward asymmetry observed at the Tevatron experiments, while being consistent with the current LHC data. These models generally lead to four-top final states at the LHC at observable levels. We compute the four-top production cross section at the LHC in a model with a massive colour octet vector as a function its mass, its width and its coupling to the top quark. Octet masses in the vicinity of the t tbar threshold are generally excluded by present limits on the production of same-sign dileptons and trileptons. Masses above 650 GeV are allowed, quite independently of the couplings, but they can be probed with the luminosity of 5 fb^-1 already collected at the LHC, up to around 800 GeV. The four-top production cross section is increased by a factor ~ 2 with sqrt{s}=8 TeV and by up to almost two orders of magnitude with sqrt{s}=14 TeV, thus greatly increasing the reach for massive gluons after the LHC energy upgrade.