Lawrence Berkeley National Laboratory

In a recent paper, Hagelstein and Pascalutsa [F. Hagelstein and V. Pascalutsa, Phys. Rev. A 91, 040502 (2015)PLRAAN1050-294710.1103/PhysRevA.91.040502] examine the error associated with an expansion of proton structure corrections to the Lamb shift in terms of moments of the charge distribution. They propose a small modification to a conventional parametrization of the proton's charge form factor and show that this can resolve the proton radius puzzle. However, while the size of the bump they add to the form factor is small, it is large compared to the total proton structure effects in the initial parametrization, yielding a final form factor that is unphysical. Reducing their modification to the point where the resulting form factor is physical does not allow for a resolution of the radius puzzle.