Single top production at linear $e^-e^+$ colliders

TL;DR

This paper analyzes the potential of future linear electron-positron colliders at various energies to study single top production, focusing on sensitivity to anomalous couplings and four-fermion operators, despite background challenges.

Contribution

It provides a preliminary assessment of single top production sensitivity to new physics operators at different collider energies, highlighting the energy dependence of operator sensitivities.

Findings

Good sensitivity to the $tbW$ vertex at 0.5 and 1 TeV despite backgrounds.

Enhanced sensitivity at 3 TeV where single top dominates.

Differential sensitivity of operators involving $ttZ$ and charged-current four-fermion interactions.

Abstract

We study single top production at linear lepton colliders with $\sqrt{s} = 0.5$, 1 and 3 TeV. A preliminary analysis shows that despite the large $t\bar t$ background at $\sqrt{s} = 0.5$ and 1 TeV it is possible to obtain a good sensitivity to the $tbW$ vertex; even more so at 3 TeV when single top becomes the dominant mode of production. Concerning the four dimension six operators involved, two of them simultaneously generate $ttZ$ couplings and their sensitivity decreases with energy. The opposite is true for the other two operators. Single top production at these machines is also useful to probe charged-current four fermion operators $e\nu bt$, some of which are related to $tbW$ operators through the equations of motion.