Improved determination of the fine structure constant based on the electron g-2 and muonium hyperfine structure

Preliminary results of two accurate determinations of the fine structure constant α based on quantum electrodynamics are reported. One is obtained from an improved evaluation of the sixth-order and eighth-order radiative corrections to the electron anomalous magnetic moment a_e. This leads to the most accurate value of α obtained thus far, with an uncertainty of about 0.005 part per million (ppm). The other is the outcome of an evaluation of the complete α²(Zα) contribution and the leading α⁴ and α³(m_e/m_μ) contributions to the hyperfine structure of the muonium ground state. This gives a value of α with an uncertainty of 0.134 ppm. These results also lead to the most accurate determination of the muon mass