How did scientists prove that quarks exist?

Karimspencer

I heard that it had something to do with acceleration in a huge accelerator in fermi-lab but where they can collide going at speeds close to the speed of light , but how does this collision help. Or is this not the way they used?

mfb

First: You cannot "prove" something in physics. It is possible to falsify a theory by experiments. But if experiments and theory agree, this does not prove the theory. If many different measurements are in agreement with predictions from this theory, it is a good theory. But it can never be proven.

How did they invent the theory? They analysed the particles produced in these collisions. In high-energy collisions, a lot of particles are produced. Before the quark model, they were all considered as elementary particles, and soon 30+ of them were known. But then they found patterns in their properties. The quark model was able to explain those patterns with just 4 (today: 6) quarks, and to predict the existence of new particles, which were found later.

It is possible to calculate a lot of properties of the particles with the quark model. And up to now, no serious deviation from these predictions was found.

Karimspencer

So could scientists predict what what are quarks made out of(if they were made out of something) by making high-energy collisions of quarks?

mfb

You cannot accelerate individual quarks. If quarks have some sub-structure, it might be possible to see this in proton-proton collisions. So far, no substructure was found, which sets lower limits for the relevant energy scale (~TeV).

Karimspencer

oh ok