Nucleons are building blocks of visible matter, and are responsible for more than 99% of the visible mass in the universe despite the fact that the discovery of the Higgs boson is almost irrelevant to the origin of the proton mass. While major progress has been made in the last two decades in understanding the proton spin puzzle discovered in the late 1980s by the European Muon Collaboration, a new proton puzzle emerged in the last several years concerning the proton charge radius, which is the

more »

... charge weighted size of the proton. In this paper we will review the latest situation concerning the proton charge radius, mass and spin, and discuss upcoming new experiments addressing these puzzles, as well as implications for new physics.