S-matrix approach to the Z resonance

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.

10 pages, Proceedings of 39th International Conference of Theoretical Physics: Matter to the Deepest, Recent Developments in Physics of Fundamental Interactions, 13-18 September 2015, Ustron, Poland; presented also at the FCC-ee meeting, February 2015, Pisa; at CALC, July 2015, JINR, Dubna; at HEPKIT, October 2015, KIT, Karlsruhe. Note added on 14 October 2016

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