Proton charge radius calculation

[edguy99]

In this link the proton charge radius is calculated based on an experiment involving a muon and a proton http://www.sps.ch/en/artikel/progresses/muonic_hydrogen_and_the_proton_radius_puzzle_20/

It talks about "In summary, we have measured the muonic hydrogen transition at a frequency of 49881.88(76) GHz which corresponds to an energy of 206.2949(32) meV [1]. The position of this line strongly disagrees with predictions (shown by the orange points in Fig. 3) which have been computed assuming the proton radius extracted from hydrogen spectroscopy and theory, and the proton radius from electron-proton scattering experiments."

Is this disagreement unique to muonic atoms or is there also disagreement from theory for a normal electron/proton atom?

 

[Bill_K]

edguy99, Since the muon is 200 times heavier than the electron, the Bohr radius for a muonic hydrogen atom is 200 times smaller. Thus the energy levels of the lowest states are much more sensitive to the properties of the proton, and in particular are affected by its charge radius. The apparent discrepancy he talks about is not yet understood.

 

[PAllen]

I raised a discussion of an aspect of this result in an earlier thread:

https://www.physicsforums.com/showthread.php?t=435990

There, the following reference was presented as explaining the finding:

http://arxiv.org/abs/1010.3421

[Edit: I notice this paper has undergone significant revision since its first preprint version and final published form. It is now less clear in its conclusions.]