Direct measurement of alpha_QED(mZ) at the FCC-ee

TL;DR

This paper proposes a method to directly measure alpha_QED at the Z boson mass scale using muon asymmetry data from FCC-ee, aiming to improve the precision of fundamental constants for testing the Standard Model and beyond.

Contribution

It introduces a novel approach to determine alpha_QED(mZ) directly from FCC-ee measurements, enhancing the accuracy of this key input parameter.

Findings

Potential for high-precision measurement of alpha_QED(mZ)

Method feasibility for FCC-ee experimental setup

Improved constraints on beyond-the-standard-model theories

Abstract

When the measurements from the FCC-ee become available, an improved determination of the standard-model "input" parameters will be needed to fully exploit the new precision data towards either constraining or fitting the parameters of beyond-the-standard-model theories. Among these input parameters is the electromagnetic coupling constant estimated at the Z mass scale, alpha_QED(mZ). The measurement of the muon forward-backward asymmetry at the FCC-ee, just below and just above the Z pole, can be used to make a direct determination of alpha_QED(mZ) with an accuracy deemed adequate for an optimal use of the FCC-ee precision data.