Pion

The pion is a particle predicted to hold protons and neutrons together within the nucleus, despite electromagnetic repulsion. It shares some properties with more massive particles and interacts with protons and neutrons, fulfilling Yukawa's prediction.
 Cecil Frank Powell England 1947 Pion

The pion is a particle predicted to hold protons and neutrons together within the nucleus, despite electromagnetic repulsion. It shares some properties with more massive particles and interacts with protons and neutrons, fulfilling Yukawa's prediction.