Single-top production and rare top interactions

TL;DR

This paper investigates how single-top production measurements at the LHC can constrain new physics effects beyond the Standard Model, especially for high-energy scale interactions, and explores top polarization as a diagnostic tool.

Contribution

It introduces a method to use single-top production data to probe high-energy new physics contact interactions and analyzes top polarization to differentiate operator structures.

Findings

Single-top production constrains new physics parameter space.

Top polarization helps distinguish operator chiralities.

Effective operators capture beyond Standard Model effects.

Abstract

The study of the top quark's properties is an important part of the LHC programme. In earlier work, we have studied the rare decay $t \to b \bar b c$, using effective operators to capture the effects of physics beyond the Standard Model. However top decay is primarily sensitive to new physics in the sub-TeV energy regime. If this new physics resides at a higher energy scale, then one needs to turn to single-top production. In this paper, we use the $s$-channel and $t$-channel single-top production measurements to constrain the new physics parameter space associated with such contact interactions. We also study the net top polarization as a means to distinguish between contributions from operators involving different fermion chiralities and Lorentz structures.