Forward-backward asymmetry in t anti-t production from flavour symmetries

TL;DR

This paper proposes models with new flavour-symmetry fields that can increase the top quark forward-backward asymmetry while remaining consistent with existing experimental constraints.

Contribution

It introduces specific new fields transforming under flavour groups that enhance asymmetry effects without conflicting with current phenomenological bounds.

Findings

Scalar colour anti-sextet field enhances asymmetry

Vector colour octet field also enhances asymmetry

Models satisfy constraints from dijet searches and other phenomenology

Abstract

We show that the forward-backward asymmetry in top quark pair production can be enhanced by fields that transform nontrivially under the flavour group and satisfy Minimal Flavour Violation, while at the same time the constraints from associated effects on the d \sigma(t anti-t)/d M_{t anti-t} distribution, dijet resonance searches, same sign top pair production and other phenomenology are satisfied. We work out two examples in detail, one where a scalar colour anti-sextet field, that is also an anti-sextet of SU(3)_U, enhances the forward-backward asymmetry, and one where the enhancement arises from a vector colour octet field that is also an octet of SU(3)_U.