Tập tin:Spin-physics-w.jpgIn this diagram representing the head-on collision of a quark (red ball) from one proton (orange ball) with a gluon (green ball) from another proton with opposite spin, spin is represented by the blue arrows circling the protons and the quark. The blue question marks circling the gluon represent the question: Are gluons polarized? Ejected from the collision are a shower of quarks and a photon of light (purple ball).
