A precise determination of top quark electro-weak couplings at the ILC operating at $\roots=500\,\GeV$

TL;DR

This study uses detailed simulations of the ILD detector at the ILC to precisely measure top quark electroweak couplings, significantly improving sensitivity over LHC expectations, at 500 GeV with polarized beams.

Contribution

It provides a detailed simulation-based analysis of top quark electroweak couplings at the ILC, including CP-conserving couplings for photon and Z boson components, with improved sensitivity.

Findings

Enhanced sensitivity to electroweak couplings compared to LHC.

Precise determination of vector, axial vector, and tensor couplings.

Effective use of polarized beams and semi-leptonic decay channels.

Abstract

Top quark production in the process $e^+e^- \rightarrow t\bar{t}$ at a future linear electron positron collider with polarised beams is a powerful tool to determine indirectly the scale of new physics. The presented study, based on a detailed simulation of the ILD detector concept, assumes a centre-of-mass energy of $\roots=500$\,GeV and a luminosity of $\mathcal{L}=500\,\invfb$ equality shared between the incoming beam polarisations of $P_{e^{-,+}} =\pm0.8,\mp0.3$. Events are selected in which the top pair decays semi-leptonically. The study comprises the cross sections, the forward-backward asymmetry and the slope of the helicity angle asymmetry. The vector, axial vector and tensorial CP conserving couplings are separately determined for the photon and the $Z^0$ component. The sensitivity to new physics would be dramatically improved with respect to what is expected from LHC for electroweak couplings.