Speaker
Description
For years, it was agreed that the radius of the proton was $0.88$ fm. A 2010 measurement using a new muonic-hydrogen spectroscopy technique reported a result of $0.84$ fm, a $5\sigma$ discrepancy with the the accepted value, launching what has come to be known as the ``proton radius puzzle''. A flurry of explanations emerged in the aftermath, ranging from new physics to incorrect analysis techniques. The 2016 PRad experiment at JLab, using a novel magnetic-spectrometer-free setup, measured the proton radius to be $0.831\pm0.014$ fm, consistent with the muonic hydrogen result and $2.7\sigma$ smaller from the combined results of all past $e-p$ scattering measurements. In this talk, I will discuss the PRad result and the upcoming PRad-II experiment that aims to achieve nearly $4$ times precision and record data at the lowest $Q^2$ ever achieved in lepton scattering ($10^{-5}$ GeV$^2$).
