Measurement of the 2S1/2–2P3/2 level splitting in muonic helium: A test of quantum electrodynamics predictions on electronic vacuum polarization

The results of a measurement of the 2S1/2-2P3/2 energy difference in the (μ4He) muonic system are presented. Full account of the experimental method as well as an up-to-date review of the pertaining theoretical predictions are given. The obtained results show a good agreement with QED predictions; the electronic vacuum polarization term of order α is checked with a relative accuracy of 5·10−3.