Henry Weller, a physicist at Duke University, and his colleagues, examined what happens when a hydrogen atom (a proton) is smashed into an atom of boron at high speed. Weller and the team at the Triangle Universities Nuclear Laboratory expected that when hydrogen and boron fused, the result would be a three alpha particles, or helium nuclei. One would be high-energy, moving fast. The other two would be low-energy ones. Experiments done in the 1980s seemed to confirm this result.
But what Weller found was different. The proton hit the boron nucleus and produced two high energy alpha particles and one that was slower. That seemed wrong until the group looked up an old result from the 1930s. At that time scientists at the Cavendish Laboratory in England had found that when a boron nucleus was hit with a proton it produced two high-energy alpha particles that separated at a certain angle, with the third one moving much more slowly.