What methods could we use to measure the diameter of sub-atomic particles. Please think of something inventive, like an indirect technique. Or name some of the lesser known techniques that have been used in the past.
Be creative, use some imagination!
The energy shifts of transitions including the s-orbitals of various isotopes of hydrogen are dependent on the proton's charge radius and are a surprisingly sensitive tool for this kind of thing. Recently this has been checked with muonic hydrogen, with surprising results.
Paper at http://dx.doi.org/10.1126/science.1230016, and references therein.
Related [physics.se] post: If the measurement of the proton size is correct and it is lower that it was expected than what are the theoretical implications?
