Precision measurements of positronium decay rate and energy level
  Positronium is an ideal system for the research of the bound state QED. New precise measurement of orthopositronium decay rate has been performed with an accuracy of 150 ppm, and the result combined with the last three is 7.0401 +- 0.0007 mu s^-1. It is the first result to validate the 2nd order correction. The Hyper Fine Splitting of positronium is sensitive to the higher order corrections of the QED prediction and also to the new physics beyond Standard Model via the quantum oscillation into virtual photon. The discrepancy of 3.5 sigma is found recently between the measured values and the QED prediction (O(alpha^3)). It might be due to the contribution of the new physics or the systematic problems in the previous measurements: (non-thermalized Ps and non-uniformity of the magnetic field). We propose new methods to measure HFS precisely without the these uncertainties. 
S.Asai, Y.Kataoka, T.Kobayashi, T.Namba, T.Suehara, G.Akimoto,   A.Ishida, M.M.Hashimoto, H.Saito, T.Idehara, M.Yoshida