Top Pair Forward-Backward Asymmetry from Loops of New Strongly Coupled Quarks

TL;DR

This paper proposes a model where new heavy quarks and scalars induce a top quark asymmetry at colliders, aligning with experimental observations and implying a non-perturbative electroweak symmetry breaking mechanism.

Contribution

It introduces a phenomenological model with flavor off-diagonal couplings that explains the observed top quark asymmetry through loop effects of new heavy quarks and scalars.

Findings

Reproduces the observed t tbar asymmetry at colliders.

Predicts heavy quarks decay mainly into t phi final states.

Suggests a non-perturbative electroweak symmetry breaking mechanism.

Abstract

We examine loop-mediated effects of new heavy quarks Q=(t',b') on t tbar production at hadron colliders, using a phenomenological model with flavor off-diagonal couplings of charged and neutral scalars phi=(phi^+-,phi^0) to Q. We show that an invariant-mass-dependent asymmetry, in the t tbar center of mass, consistent with those recently reported by the CDF collaboration can be obtained for quark masses around 350-500 GeV, scalar masses of order 100-200 GeV, and modest to strong Yukawa couplings. The requisite strong interactions suggest a non-perturbative electroweak symmetry breaking mechanism and composite states at the weak scale. A typical prediction of this framework is that the new heavy quarks decay dominantly into t phi final states.