How Quarks Were Discovered

The first major step in solving the particle zoo came from Murray Gell-Mann, a Caltech theorist who had already spent years hunting for order inside the particle zoo.

In 1961, he had found a pattern he called the Eightfold Way, a way of arranging the known hadrons into neat octets based on their properties.

For context, at the time, physicists had already split the known particles into two categories: hadrons, which I had just mentioned, and leptons.

The difference between the two was whether or not they interacted with the strong nuclear force.

Larger particles like protons and neutrons, when smashed together in accelerators, created showers of new particles.

But lighter particles, like electrons and neutrinos, didn't break apart, but rather deflected unchanged or transformed into another small particle entirely.

Those leptons were separated and organized fairly easily.

When regarding the hadrons though, the issues I pointed out earlier reigned supreme.

In 1949, Enrico Fermi and Yang Chen-Ning proposed the Fermi-Yang model, assuming that there were four fundamental baryons that made up mesons: the proton, the neutron, the antiproton, and the antineutron.

The math of colliding these baryons consisted essentially of multiplying two vectors, a proton-neutron vector and its antimatter equivalent, to get a two-by-two matrix of all possible combinations of the interacting four particles.

The resulting lighter particles are called mesons, and the heavier particles that were in the multiplication are called baryons.

Well, what physicists extracted from this multiplication in the pre-1961 era was that there are four possible mesons, three pions, all with varying electric charges, and a fourth neutral meson.

By this math, that's all you should expect to find when interacting these four particles together.

But as I've said, there were a hundred plus particles being found, both new baryons and new mesons.

Not only that, for some of these particles, when decaying from existence, wouldn't interact with the strong force at all, causing the weak force to take over and therefore causing said particles to take longer than expected to decay.

This was very strange to physicists.

So strange, in fact, that Gell-Mann, among three others, in 1953 invented a new trait to describe such a behavior and named it just that, strangeness.

Throughout the years, he assigned and predicted particles to have a strangeness ranging from plus three to minus three based on which particles always showed up together and also based on what number made the math add up.

Adding a new characteristic, though, meant changing the matrix math entirely.

In 1956, a Japanese physicist named Shoichi Sakata tried to fix this by introducing a three-by-three matrix system.

He realized that if you added a third fundamental baryon, the lambda baryon, to account for strangeness to the end of the proton-neutron vectors, you could track both electric charge and strangeness at once.

Sakata's model was a breakthrough, and upon inception, it described mesons beautifully.

The math worked out to create a family of eight mesons and another single meson that all matched experimental data.

But it still had several flaws when it came to predicting the other baryons in the zoo.

Sakata tried to explain these heavier baryons by saying that to create new, heavier baryons, you would have to interact two of the fundamental baryons and one fundamental antibaryon.