A Missing Charm

With all of the discovered particles, Glashow, Salam, and Weinberg created the Standard Model, a theory that explains the fundamental particles and forces. The Standard Model contained three quarks, the up and down quarks, the up with an electric charge of +2/3, the down with -1/3, and the strange quark. The strange quark was the particle that had the property of strangeness.

However, three quarks were not enough. The mathematical theory behind the Standard Model required the existence of a fourth quark, the charm quark. Yet, no particle containing such a quark had ever been seen.

Then in 1974, an experiment led by Samuel Ting and another by Burton Richter (The Nobel Prize in Physics 1976) simultaneously discovered a particle that contained the missing charm quark. One called it J and the other psi. It is now known as the J/psi particle.