In proton-proton smashups, more neutrons scatter to the right than the left relative to the proton spin direction. That was the accepted wisdom, and scientists thought the pattern would hold even when the protons struck larger nuclei. Painstaking new research shows that’s not the case. Scientists analyzed collisions of spinning protons with different-sized atomic nuclei at the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). They found that increasing the size of the nucleus “target” caused neutrons scattering from these collisions to switch their directional “preference” from rightward to leftward. The results suggest that the mechanisms producing the scattered neutrons differ depending on the size of the target.