On the Precise Determination of the Fermi Coupling Constant from the Muon Lifetime

TL;DR

This paper refines the measurement of the Fermi coupling constant G_F by analyzing recent 2-loop QED corrections and experimental plans to measure the muon lifetime with sub-ppm precision, discussing uncertainties and electroweak integration.

Contribution

It provides a detailed calculation of 2-loop QED corrections and assesses uncertainties in determining G_F from muon lifetime measurements.

Findings

QED corrections significantly impact G_F precision

Uncertainties are dominated by theoretical and experimental factors

Incorporation of G_F into the Standard Model is discussed

Abstract

The determination of the Fermi coupling constant, G_F, is examined in the light of recently calculated 2-loop QED corrections and planned experiments to measure the muon lifetime to a level below 1ppm. The methods used in the calculation of the QED corrections are described in detail. Sources of the dominant theoretical and experimental uncertainties are identified. Finally the incorporation of G_F into analyses using the full electroweak Standard Model is discussed.