[PAST EVENT] Physics Colloquium
Recent atomic physics measurements using the Lamb shift in Muonic hydrogen have determined the proton's charge radius to be 0.84 fm, while the radius determined from atomic hydrogen Lamb shift and modern electron scattering measurements give a value of 0.88 fm. As the proton has only one true radius, this systematic difference in the radius from different measurement techniques has become known as the proton radius puzzle. I will discuss the strengths and weaknesses of the Muonic hydrogen measurements compared to atomic hydrogen. I will also summarize the history of the electron results, starting from the 1963 review
article on nuclear physics electron scattering data by Hand et al. with its 0.81(1)fm
standard dipole radius, and track the evolution of the proton charge radius up to the
recent 0.88(1)fm results from Mainz. I will then discuss the statistical methods that
were used by groups in Virginia (JLab, UVA, and W&M) that yield an electron scattering
result that is in agreement with the Muonic hydrogen results. Finally, I will discuss
how these results could bring about a change to the Rydberg constant.