Signatures of toponium formation in LHC run 2 data

TL;DR

This paper explores the potential formation of toponium, a top-antitop bound state, at the LHC, analyzing deviations in top quark pair production and proposing a method to detect toponium through di-lepton decay channels.

Contribution

It introduces the concept of toponium formation in LHC data, analyzes its production signatures, and proposes a reconstruction method for its detection in di-lepton events.

Findings

Toponium production could explain observed excesses in certain phase space regions.

Toponium contributes only 0.8% to total top-pair production at 13 TeV.

Distinct angular and invariant mass correlations favor toponium detection.

Abstract

We study reported deviations between observations and theoretical predictions associated with the production of a pair of di-leptonically decaying top quarks at the LHC, and we examine the possibility that they reflect a signal of toponium formation. We investigate the production by gluon fusion of a color-singlet spin-0 toponium $\eta_t$ bound state of a top and anti-top quark, that then decays di-leptonically ($gg\to\eta_t \to \bar\ell \ell b \bar{b} \nu \bar{\nu}$). We find strong correlations favoring the production of di-lepton systems featuring a small angular separation in azimuth and a small invariant mass. Although toponium production only contributes to 0.8% of the total top-quark pair-production cross section at the 13 TeV LHC, there is a possibility that it can account for observed excesses in the narrow edges of phase space. We propose a method to discover toponium formation by `reconstructing' both its top and anti-top quark constituents in the di-lepton channel.