Quantum physics is a scary field. It holds so many answers, and almost none of those are truly understandable by the general public. This results in theories like the idea that CERN and the LHC have “destroyed our universe,” or that “The LHC creates black holes that will kill us all.” This is as much speculation as it is simple ignorance. This is why I chose to write this series: to enlighten the general public about the truths of Quantum Physics, and shed some light on the truths behind the ignorance. Without further adieu, here is part 2 of Unlocking the Secrets of The Standard Model: Leptons.
Leptons are a reclusive bunch. They like to hang out by themselves, and tend to stay away from one another. This is why they hold such prevalence to the field of Quantum Physics. If we can observe some different kind of particles, most of which are either irregular, or try to repel (or annihilate) each other, we can gain some real insights into the world of Quantum Physics. There are 6 different types of leptons that are included in the standard model. Before I cover these different types of leptons, we should first talk about the definition of a lepton, and the definition of a fermion. A fermion is “a subatomic particle, such as a nucleon, that has half-integral spin and follows the statistical description given by Fermi and Dirac.” This simply means that a fermion is any particle with ½ spin, such as quarks, and leptons. In fact, quarks and leptons are the two subcategories of fermions. Since we’ve already covered quarks, we can move on to the definition of a lepton. A lepton is defined as “Any ½ integer spin particle that does not undergo strong interactions.” I will be covering the strong interaction in a later post, so we can ignore that for the moment.
Now that we know what leptons are, we can talk about the six different flavors that we know of. The first 3 that we will cover are the charged leptons. The first charged lepton is the ever-famous electron. Most people know about what an electron is, but since this post is mainly geared toward enlightening others about these things, I will give a brief synopsis. The electron is arguably the most important particle ever discovered. Like all other leptons, it has a half integer spin, and is negatively charged. The electron orbits around the outside of the atomic nucleus, being held in just the right place by the charge of the protons in the center. That’s pretty much the fundamentals of the electron.
The next particle is the muon, which is the second of the charged leptons. A muon is simply a much larger and more unstable electron. It is about 207 times as large as an electron, and holds a similar charge. They mostly produced by cosmic rays, and in particle accelerators. Because they are so massive, the are not produced by normal radioactive decay, unlike most other particles. Muons have no known use to any kind of interaction, other than their strange style of decay.
The final charged lepton is known as the tau, or tauon. The tauon has a negative electrical charge, and, as all other leptons, has a half integer spin. The Tauon again can be thought of as a much larger electron, considering the fact that it is interacts in mostly the same way. The only difference is that the tauon is much, much more massive, and much more deeply penetrating. Tauons also have very strange decay properties, much like those of a muon, but with different particles.
The final 3 leptons are known as neutrinos, and they have no charge. Each of the 3 charged leptons has a neutrino counterpart. The three types of neutrinos are: The electron neutrino, the muon neutrino, and the tau neutrino. A neutrino has no charge, and a near-zero mass, making it extremely hard to detect without the right kind of equipment or experiment. The most common way that neutrinos are produced is in the decay of other particles, specifically the particles that each neutrino is named after. Each neutrino is produced either in a star, in some kind of cosmic reaction, or in particle decay.
That covers all of the leptons! If you have any questions, suggestion, or feedback, feel free to let me know! Stay with us as the wonderful world of Quantum Physics is rediscovered, one piece at a time!