Atomic physics determination of the fine structure constant

• 来源期刊: 国家科学评论（英文版）
• 年，卷（期）: 2020,（12）
• 所属期刊栏目: Special Topic: Precision Measurement Physics
• 页码范围: 1797-1798
• 页数: 2页
• 语种: 英文
• DOI: 10.1093/nsr/nwz186

摘要

The fine structure constant α is a funda-mental physical constant that describes the electromagnetic interaction between charged particles and serves as the cou-pling constant of quantum electrody-namics(QED).It is dimensionless and thus remains the same under all systems of units.It is worth noting that α cannot be calculated by QED itself;it must be de-termined experimentally,often with the help of QED directly or indirectly.Deter-minations of α from different sources can be used to test QED and other sectors of the Standard Model of particle physics,provided both theory and experiment can reach a sufficiently high precision.How-ever,one cannot both test QED and mea-sure α simultaneously,and so at least two independent measurements are required.One of the two most precise determi-nations of α so far is from the anoma-lous magnetic moment orge-2 of the electron,which yields α to an accuracy of 0.24 ppb(parts per billion)[1].The other one comes from the cesium re-coil experiment that gives rise to α at 0.20 ppb[2].Thege-2 determination of α involves a monumental QED cal-culation,whereas the Cs recoil one re-lies on QED only in an indirect way,be-cause the Rydberg constant Roo used in the Cs recoil determination was already established to very high precision by hydrogen and deuterium transition fre-quencies together with their correspond-ing QED calculations.However,these two determinations of α have a 2.5σ dis-crepancy that may have some implica-tions for new physics beyond the Stan-dard Model[2].From a metrology view-point,with the adoption of the 2019 re-definition of the SI base units,a more pre-cise value ofα would mean a more precise value of the electron mass me according to Roo =α2me(c/4πh).