Exploring the $t\bar{t}$ threshold at an electron-positron collider

TL;DR

This study evaluates the potential of future electron-positron colliders, specifically the CEPC, to precisely measure top-quark properties and fundamental constants through threshold scans, significantly surpassing LHC precision.

Contribution

First comprehensive prospect analysis of simultaneous top-quark parameter measurements at an electron-positron collider using the latest CEPC detector design.

Findings

Top-quark mass can be measured with a few MeV precision.

Measurement precision exceeds that of the HL-LHC by nearly two orders of magnitude.

Theoretical uncertainties currently limit the measurement accuracy.

Abstract

Future electron-positron colliders offer a unique opportunity for high-precision measurements of the top-quark mass, width, strong coupling constant, and top-quark Yukawa coupling via a scan of the $t\bar{t}$ threshold. We present the first prospect study of the simultaneous determination of these parameters, incorporating the latest reference detector design for the Circular Electron-Positron Collider (CEPC). We find that the precision of the top-quark mass measurement can reach a few MeV excluding the theoretical uncertainty on the cross-section, which is nearly two orders of magnitude better than the high-luminosity LHC (HL-LHC) projections. The current theoretical uncertainty of the cross-section calculation is the limiting factor.