Flipping t tbar asymmetries at the Tevatron and the LHC

TL;DR

This paper explores the relationship between charge asymmetry at the LHC and forward-backward asymmetry at the Tevatron, showing they can differ significantly under new physics models, and identifies observables for future NP detection.

Contribution

It demonstrates that A_C and A_FB are not necessarily correlated and can have opposite signs, challenging previous assumptions and suggesting new observables for NP effects.

Findings

A_C and A_FB can have opposite signs under certain NP models.

Small A_C at LHC does not exclude NP explanations for large A_FB at Tevatron.

b bbar asymmetry and top polarization are promising NP observables.

Abstract

We show that the charge asymmetry in t tbar production at the LHC, A_C, and the forward-backward asymmetry at the Tevatron, A_FB, are in general not tightly correlated. They can even have opposite signs, if the underlying new physics (NP) model is general enough. We demonstrate this using two examples of NP: a light axigluon, and a vector that is a color octet and electroweak triplet. The small value of A_C measured at the LHC is thus shown not to exclude a NP interpretation of the anomalously large A_FB at the Tevatron. We identify two observables where significant NP effects are still expected at the Tevatron and the LHC, the b bbar production forward-backward asymmetry and spin polarizations of the pair-produced tops and anti-tops.