Theory of the 2S-2P Lamb shift and 2S hyperfine splitting in muonic   hydrogen
  The 7 standard deviations between the proton rms charge radius from muonic hydrogen and the CODATA-10 value from hydrogen spectroscopy and electron-scattering has caused considerable discussions. Here, we review the theory of the 2S-2P Lamb shift and 2S hyperfine splitting in muonic hydrogen combining the published contributions and theoretical approaches. The prediction of these quantities is necessary for the determination of both proton charge and Zemach radii from the two 2S-2P transition frequencies measured in muonic hydrogen. 
Aldo Antognini, Franz Kottmann, Fran\c{c}ois Biraben, Paul Indelicato,   Fran\c{c}ois Nez and Randolf Pohl
physics.atom-ph