Light Colored Scalar as Messenger of Up-Quark Flavor Dynamics in Grand Unified Theories

TL;DR

This paper explores how a light colored scalar, predicted by grand unified theories, could explain anomalies in top quark production and predicts its signatures in rare top decays, linking low-energy observations to high-energy physics.

Contribution

It systematically constrains the Yukawa couplings of a colored scalar in GUT models using experimental data and predicts observable signatures in top quark decays.

Findings

Constraints on Yukawa couplings from D0--D0bar oscillations and collider data.

Predictions of rare top decay signatures.

High-energy Yukawa coupling constraints from low-energy data.

Abstract

The measured forward-backward asymmetry in the t tbar production at the Tevatron might be explained by the additional exchange of a colored weak singlet scalar. Such state appears in some of the grand unified theories and its interactions with the up-quarks are purely antisymmetric in flavor space. We systematically investigate the resulting impact on charm and top quark physics. The constraints on the relevant Yukawa couplings come from the experimentally measured observables related to D0--D0bar oscillations, as well as di-jet and single top production measurements at the Tevatron. After fully constraining the relevant Yukawa couplings, we predict possible signatures of this model in rare top quark decays. In a class of grand unified models we demonstrate how the obtained information enables to constrain the Yukawa couplings of the up-quarks at very high energy scale.