Top quark mass measurement in radiative events at electron-positron colliders

TL;DR

This paper explores the potential of future linear electron-positron colliders to measure the top quark mass precisely using radiative events, incorporating advanced calculations and realistic collider scenarios.

Contribution

It presents a matched calculation of the top pair production with an energetic photon, enabling precise top mass measurements and testing mass evolution at different scales.

Findings

Top quark mass can be measured with 110 MeV precision at CLIC.

Top quark mass can be measured with 150 MeV precision at ILC.

Radiative events allow testing the MSR mass evolution.

Abstract

In this letter, we evaluate potential of linear $e^+e^-$ colliders to measure the top quark mass in radiative events and in a suitable short-distance scheme. We present a calculation of the differential cross section for production of a top quark pair in association with an energetic photon from initial state radiation, as a function of the invariant mass of the $t\bar{t}$ system. This {\it matched} calculation includes the QCD enhancement of the cross section around the $t\bar{t}$ production threshold and remains valid in the continuum well above the threshold. The uncertainty in the top mass determination is evaluated in realistic operating scenarios for the Compact Linear Collider (CLIC) and the International Linear Collider (ILC), including the statistical uncertainty and the theoretical and experimental systematic uncertainties. With this method, the top quark mass can be determined with a precision of $110$ MeV in the initial stage of CLIC, with $1$ ab$^{-1}$ at $\sqrt{s} =$ 380 GeV, and with a precision of approximately $150$ MeV at the ILC, with $L = 4$ ab$^{-1}$ at $\sqrt{s}= 500$ GeV. Radiative events allow measurements of the top quark mass at different renormalization scales, and we demonstrate that such a measurement can yield a statistically significant test of the evolution of the MSR mass $m_t^{\rm MSR}(R)$ for scales $R< m_t$.