The proton charge radius

The proton is responsible for about half the mass in our personal lives. So it perhaps surprising that little known how got here or bound from its fundamental quark and gluon constituents. This uncertainty largest source of error to extracting some constants nature. One observable probes internal structure tests theoretical description charge radius. radius sensitive quantum electrodynamics chromodynamics helps constrain new physics. review presents current status among four types experiments measure radius: electron scattering, muon electronic hydrogen spectroscopy, muonic spectroscopy.