The other day, I noticed that “hadrons” had been mentioned in my daughter's eighth grade science homework. I had heard of the Large Hadron Collider and the quest for the Higgs boson, but I have to admit that I had not really been paying attention. So now I wondered, what the heck is a hadron?
When I was in high school, I learned that atoms were made of protons, neutrons and electrons, and that was it. Since then, particle physicists have found all kinds of subatomic particles. In this post, I'm going to focus on what I have discovered about hadrons and associated subatomic particles.
One way to define hadrons (pronounced, by the way, like, "I've been had”) is that they are particles with which the strong force interacts. The strong force is one of the four fundamental forces of nature, along with gravity, electromagnetism, and the weak force (not to be confused with The Force in Star Wars). The strong force keeps particles like protons and neutrons together and within the nucleus through massless particles called gluons.
Another way to describe hadrons is by their composition. Quarks are key ingredients in the hadron recipe. Quarks come in a six flavours. This is not flavour as in taste, but physicists apparently got tired of saying "types." The six flavours of quarks are up, down, strange, charm, top, and bottom. Among other properties, they have different colours of charge, such as red, green and blue, though these are more metaphorical colours rather than ones you could actually see.
Antiquarks are the anti-particles of quarks. Anti-particles are antimatter, which I had thought was just science fiction, but is actually an important thing. They also have anti-colour charges. Quarks and anti-quarks are the only particles that interact with all four fundamental forces.
Types of Hadrons
Hadrons all include gluons, which transmit the strong force, and quark-antiquark pairs Hadrons can be further subdivided according to what else they contain. For example, protons and neutrons are considered baryons because they have three valence quarks. Their combinations of up and down quarks, the lightest and most stable quarks, account for the positive charge of protons and the neutral charge of neutrons.
Large Hadron Collider
At first I wondered if this collided large hadrons but since hadrons are all relative to us, teeny tiny, that would be somewhat of a misnomer. It seems to be named this way because it consists of a large tunnel that is 27km in circumference, which makes it the largest machine in the world at the moment. It's buried under the border of France and Switzerland. They use large amounts of energy to smash hadrons and other particles together and find out what happens.
Learning the name of a thing runs the risk of making you think you know it and stopping your thinking. In an age of search engines though, the name of a thing can give you a way in to finding out more. Perhaps you and I can develop a greater appreciation for subatomic particles, the way some people cultivate a taste for wine or art. For example, if you live in the Lower Mainland, you could take a tour at TRIUMF, Canada's particle accelerator at UBC.
If you have any particle-larly smashing ideas about particles, please share them in the comments below.