OLYMPUS experiment sheds light on structure of protons
A mystery concerning the structure of protons is a step closer to being solved, thanks to a seven-year experiment led by researchers at MIT. For many years researchers have probed the structure of protons — subatomic particles with a positive charge — by bombarding them with electrons and examining the intensity of the scattered electrons at different angles. In this way they have attempted to determine how the proton’s electric charge and magnetization are distributed. These experiments had previously led researchers to assume that the electric and magnetic charge distributions are the same, and that one photon — an elementary particle of light — is exchanged when the protons interact with the bombarding electrons. However, in the early 2000s, researchers began to carry out experiments using polarized electron beams, which measure electron-proton elastic scattering using the spin of the protons and electrons. These experiments revealed that the ratio of electric to magnetic charge...