Katherine Mesick, JLAB

In 2010, a precise measurement of the proton’s charge radius using
muonic hydrogen found with high significance a 4% smaller value than
expected from previous measurements using electrons.  The discrepancy
is now greater than 7 standard deviations, and while many theories
have been proposed to explain the difference, none is generally
favored as a resolution to the puzzle.  Possible solutions to the
puzzle include new physics beyond the Standard Model, new novel
hadronic physics, or issues in the experimental extractions of the
radius.  This talk will review the proton radius puzzle, discuss
possible solutions to the puzzle, and will provide an overview of the
experiments aimed at solving the puzzle.