S-matrix approach to the Z resonance

TL;DR

This paper discusses a model-independent S-matrix approach for analyzing the Z boson resonance at future high-precision electron-positron colliders, emphasizing the importance of accurate photonic corrections.

Contribution

It introduces the S-matrix method for Z resonance analysis and details the SMATASY/ZFITTER tools for precise, model-independent measurements of Z boson parameters.

Findings

Provides a framework for model-independent Z parameter extraction.

Highlights the importance of photonic correction modeling.

Prepares for high-precision Z resonance measurements at FCC-ee.

Abstract

The proposed $e^+e^-$-collider FCC-ee aims at an unprecedented accuracy for $e^+e^-$ collisions into fermion pairs at the $Z$ peak, based on about $10^{13}$ events. The S-matrix approach to the $Z$ boson line shape allows the model-independent quantitative description of the reaction $e^+e^- \to {\bar f}f$ around the $Z$ peak in terms of few parameters, among them the mass $M_Z$ and width $\Gamma_Z$ of the $Z$-boson. While weak and strong corrections remain "black", a careful theoretical description of the photonic interactions is mandatory. I introduce the method and describe applications and the analysis tool SMATASY/ZFITTER.