$A^t_{FB}$ Meets LHC

TL;DR

This paper evaluates the LHC's potential to measure the top quark forward-central-charge asymmetry and discover new physics, such as resonances or contact interactions, to clarify discrepancies observed at the Tevatron.

Contribution

It demonstrates that the LHC can measure the asymmetry at 5σ with 60 fb$^{-1}$ and can detect TeV-scale resonances and contact interactions, providing insights into the Tevatron anomaly.

Findings

LHC can measure the asymmetry at 5σ with 60 fb$^{-1}$ at 14 TeV.

Early LHC runs at 7 TeV could detect asymmetry enhancements.

TeV-scale color octet resonances and contact interactions are discoverable.

Abstract

The recent Tevatron measurement of the forward-backward asymmetry of the top quark shows an intriguing discrepancy with Standard Model expectations, particularly at large $\ttbar$ invariant masses. Measurements of this quantity are subtle at the LHC, due to its $pp$ initial state, however, one can define a forward-central-charge asymmetry which captures the physics. We study the capability of the LHC to measure this asymmetry and find that within the SM a measurement at the $5\sigma$ level is possible with roughly 60 fb$^{-1}$ at $\sqrt{s} = 14$ TeV. If nature realizes a model which enhances the asymmetry (as is necessary to explain the Tevatron measurements), a significant difference from zero can be observed much earlier, perhaps even during early LHC running at $\sqrt{s} = 7$ TeV. We further explore the capabilities of the 7 TeV LHC to discover resonances or contact interactions which modify the $\ttbar$ invariant mass distribution using recent boosted top tagging techniques. We find that TeV-scale color octet resonances can be discovered, even with small coupling strengths and that contact interactions can be probed at scales exceeding 6 TeV. Overall, the LHC has good potential to clarify the situation with regards to the Tevatron forward-backward measurement.