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The Beginners Guide to Sub-Atomic Particles
by : Lim Weng Khong

Ah, neutrinos, quarks and tachyons. Weird stuff huh? So what are these thingies anyway? To cut things short, these stuff are particles are make up atoms (and we thought atoms were small enough). Actually, back in the old days, the Greeks had the idea that everything was made up of various types of tiny little matter that were called atoms (the word atom came from the word 'atomos' meaning indivisible in Greek). This means that you can't split an atom in two because they're the smallest as things can be. Boy were they wrong. Experiments conducted by scientists such as JJ Thomson, Ernest Rutherford and James Chadwick determined that the atom actually consisted of protons, electrons and neutrons (as we have learnt in Fizik, haha!). However, things didn't stop there. Here's a look at even smaller particles that have been discovered!

Quarks : During experimental collisions between particles (such as protons and protons or protons and electrons), scientists discovered that in the aftermath of the collisions (when those two particles collided, they broke up into smaller parts, just like what happens in an auto accident), there existed smaller particles which they decided to call Quarks. Quarks consist of six 'flavors' (see, the scientists are getting more whimsical!), namely Up, Down, Top, Bottom, Strange and Charmed. Each flavor comes in three colors, which are Red, Green and Blue. In addition, quarks are sociable animals and are never found alone. Protons are made of 2 Up and 1 Down quark whereas neutrons are made up of 2 Down and 1 Up quark. Particles consisting of other types of quarks can be created but these have a much greater mass and rapidly decay into protons and neutrons.

Leptons : Another type of matter particles are leptons. Leptons exist in six types, three with electrical charge and three without. The electron is an example of a charged lepton. The others are the muon and tau, which are more massive. The other three are harder to locate because they are chargeless and have very little mass. Whereas the quarks must exist in the form of composite particles (must group together), leptons are solitary particles. There are also antileptons (which are the antimatter counterpart of leptons). The name positron is given to the anti-electron.

Hadrons, Baryons and Mesons : Since quarks form groups with other quarks and are never lone, they always form composite particles called Hadrons. The Hadrons, in turn consist of two groups called Baryons and Mesons. Baryons are hadrons which are made up of three quarks. Electrons and neutrons are baryons because they consist of Up-Up-Down and Down-Down-Up quarks respectively. Mesons, on the other hand are made up of a pair of quark and antiquark. For example, a pion is made up of an up quark and a down antiquark. An antimeson would have the quark and antiquark switched. So this means that an antipion would be made up of a down quark and up antiquark.

What is antimatter?
It has been discovered that for all matter particles, there has to exist a corresponding antimatter particle (or antiparticle). These antiparticles look and behave exactly like corresponding matter particles. The only difference is that they have totally opposite charges. As we all know, the proton is a positively charged particle. Therefore, the antiproton is negatively charged. Because matter and antimatter have the same mass, both are equally affected by gravity. What makes them so interesting to scientists is that when a particle and an antiparticle come together, they annihilate and convert into pure energy! In the future, these collisions can be harnessed to produce energy for the masses.

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