Scalar-mediated $t\bar t$ forward-backward asymmetry

TL;DR

This paper investigates a scalar-mediated mechanism, specifically a color-singlet weak-doublet scalar in the t-channel, to explain the observed large forward-backward asymmetry in top-antitop production, consistent with existing measurements.

Contribution

It identifies the specific scalar exchange mechanism compatible with experimental data and analyzes its implications for top pair asymmetry and collider constraints.

Findings

Only the t-channel exchange of a color-singlet weak-doublet scalar explains the asymmetry.

The proposed scalar model aligns with current $tar t$ cross section measurements.

No significant deviation in $tar t$ production is expected at the LHC.

Abstract

A large forward-backward asymmetry in $t\bar t$ production, for large invariant mass of the $t\bar t$ system, has been recently observed by the CDF collaboration. Among the scalar mediated mechanisms that can explain such a large asymmetry, only the t-channel exchange of a color-singlet weak-doublet scalar is consistent with both differential and integrated $t\bar t$ cross section measurements. Constraints from flavor changing processes dictate a very specific structure for the Yukawa couplings of such a new scalar. No sizable deviation in the differential or integrated $t\bar t$ production cross section is expected at the LHC.