Kazuki Yoshida

Inside an atomic nucleus, particles aren't just tossed together any which way. Sometimes two protons and two neutrons huddle into a tight quartet — a mini-collective known as an alpha cluster. Think of it as a family that sticks together in a crowded building. Knocking this quartet out of the nucleus and seeing how it lived there is a job for a fast proton.

The carbon nucleus was long imagined as a uniform ball of protons and neutrons, evenly mixed like dough. But physicist George Gamow suspected otherwise: particles inside might group into tiny, sturdy blocks — helium nuclei, or alpha particles.