Quarks and Leptons – the Stuff of Matter

JUNE 18, 2012 , Jason Carr | Quarks and Leptons – the Stuff of Matter | Wired Cosmos.

Physics is the study of matter, its composition and energy. Scientists have attempted to explain how matter comes into existence and how it operates for thousands of years. It is now known that all matter is composed quarks and leptons, elementary particles that combine in different ways to create the matter we live with everyday.

What Are Quarks?

Quarks are the minute particles that make up protons and neutrons. Quarks generally occur in groups of 2 or 3 to create different kinds of particles. Quarks are said to have different “flavors, “ known as up, down, strange, charm, bottom and top. The “up” and “down” quarks are the lightest. The “strange” quark was named so because of the strangely long lifetime of the particle in which it was first found. The “charm” quark was named on a whim and was discovered at two labs around the same time, at the Stanford Linear Accelerator Center and the Brook haven National Laboratory. The “bottom” quark was discovered at the Fermi National Laboratory. The “top” quark is the most massive of all the quarks. It was also discovered at the Fermi Lab. For each quark, there is a corresponding anti-quark.

What Are Leptons?

The word “lepton” comes from the Green language, meaning “small mass.” It is now known that this label is not always an accurate description for leptons. The lepton is another type of elementary particle. Scientists have identified 6 types of leptons. Three of these have electrical charge and three do not. One of the best-known types of leptons is the electron people know in the model of the atom. This type of lepton has an electrical charge. The other two charged leptons are the muon and the tau, which have more mass than electrons. The other three leptons are neutrinos. Where quarks are sociable and hang out in groups, leptons are solitary particles. The anti-electron is called a positron.

Anti-quarks and Anti-leptons

For every identified particle there is also an anti-particle that composes what is known as anti-matter. Anti-particles behave like their corresponding matter particles, but they have the opposite charge. An anti-particle even has the same mass as its matter particle. Though the concepts of anti-matter and anti-particles may be difficult to imagine, experiments in physics clearly indicate that that anti-matter exists. However, we do not see it on the material level as we do matter. Science has not yet determined why this is so. They do know, however, that when particles and anti-particles meet, they become pure energy.

How Matter Particles Interact

Particles like quarks and leptons interact due to an exchange of force carrier particles. These are particles that are very different from the quarks and leptons. For instance, the photon is a force carrier particle that has an electrical charge. It can be produced or affected by other particles that have electrical charge. In contrast, neutrinos that have no electrical charge cannot absorb or produce photons, so they are not affected by photons’ electromagnetic excitation. The particle must be able to absorb or produce the force carrier particle or it will not interact with it. Another type of force carrier particle, the gluon, causes the excitation of the strong forces between quarks. The existence of some types of force carrier particles, like the graviton, is not yet proven but is strongly suggested by experimentation.