H. Klest

A beam of electrons, twisted like a corkscrew, slams into a proton. From the collision point, pairs of particles, a positive and a neutral pion, fly out. For the first time, physicists measured how often such pairs scatter at different angles when the electron's spin points left or right.

The proton isn't a solid ball; it's more like a tight tangle of quarks and gluons. Gluons are the particles that carry the strong force — a kind of glue that holds quarks together. But this glue doesn't just connect; it presses. In the J/ψ-007 experiment at Jefferson Lab, a beam of photons was aimed at protons.