Credit: Brookhaven National Laboratory
Neutrons produced when a spin-aligned (polarized) proton collides with another proton come out with a slight rightward-skew preference. But when the polarized proton collides with a much larger gold nucleus, the neutrons' directional preference becomes larger and switches to the left. These surprising results imply that the mechanisms producing particles along the beam direction may be very different in these two types of collisions.