State of the art in the determination of the fine structure constant: test of Quantum Electrodynamics and determination of h/mu

TL;DR

This paper reviews methods for precisely determining the fine structure constant, highlighting recent experimental and theoretical advances that test quantum electrodynamics and aid in defining fundamental constants and units.

Contribution

It presents the Paris experiment measuring rubidium atom recoil to determine alpha and discusses recent improvements in QED calculations and measurements impacting fundamental constants.

Findings

Improved measurement of the fine structure constant.

Enhanced QED calculations of the electron anomaly.

Potential to precisely determine h/mu ratio.

Abstract

The fine structure constant $\alpha$ has a particular status in physics. Its precise determination is required to test the quantum electrodynamics (QED) theory. The constant $\alpha$ is also a keystone for the determination of other fundamental physical constants, especially the ones involved in the framework of the future International System of units. This paper presents Paris experiment, where the fine structure constant is determined by measuring the recoil velocity of a rubidium atom when it absorbs a photon. The impact of the recent improvement of QED calculations of the electron moment anomaly and the recent measurement of the cesium atom recoil at Berkeley will be discussed. The opportunity to provide a precise value of the ratio $h/m_{\mathrm{u}}$ between the Planck constant and the atomic mass constant will be investigated.