Massive Spin-2 States as the Origin of the Top Quark Forward-Backward Asymmetry

TL;DR

This paper proposes that a new massive spin-2 particle with flavor-violating couplings to quarks can explain the large top quark forward-backward asymmetry observed experimentally, fitting the data across different energy scales.

Contribution

It introduces a novel model with a massive spin-2 state to account for the asymmetry, highlighting the role of graviton-like couplings and energy sensitivity.

Findings

The model can reproduce the observed asymmetry in the high mass bin.

A large parameter space is consistent with experimental constraints.

The effects are highly sensitive to energy scales due to graviton-like couplings.

Abstract

We show that the anomalously large top quark forward-backward asymmetry observed by CDF and D\O\, can naturally be accommodated in models with flavor-violating couplings of a new massive spin-2 state to quarks. Regardless of its origin, the lowest-order couplings of a spin-2 boson to fermions are analogous to the coupling of the graviton to energy/momentum, leading to strong sensitivity of the effects associated with its virtual exchange to the energy scales at hand. Precisely due to this fact, the observed dependence of the asymmetry on the $t\bar t$ invariant mass fits nicely into the proposed framework. In particular, we find a vast parameter space which can lead to the central value for the observed forward-backward asymmetry in the high mass bin, while being in accord with all of the existing experimental constraints.