Question: what is a top quark ?

Kathryn Coldham answered on 11 Nov 2018: last edited 11 Nov 2018 12:53 pm

Great question Alyssa!

A quark is a type of elementary particle, which is a particle that cannot be broken down into smaller pieces, and is described by a clever theory known as the Standard Model. There are six quarks, all with funny names: up, down, strange, charm, top and bottom! The top quark was found in 1995 and is the heaviest of all of the quarks, with a mass that is about 170 times that of the proton! Because it is so heavy, we need to use a large amount of energy in order to make one. So the Large Hadron Collider (the largest particle accelerator in the world) is perfect to use to study this particle further because it smashes particles together at record-breaking energies.

Its large mass also means that it has a short lifetime, which is the time that a particle can exist for before it decays into other particles. For example, in nearly all cases, the top quark decays into two particles: a W boson and a bottom quark. In fact, the top quark’s lifetime is about a millionth of a millionth of a millionth of a millionth of a second….an incredibly tiny amount of time! This short lifetime means that it decays before a process called hadronisation can take place. Hadronisation is when a single quark produces a jet (a tight cone of particles). Because hadronisation doesn’t happen to the top quark, this makes it very unique so it is very interesting to study it! For example, scientists are trying to understand why the top quark is so heavy, they are trying to find and learn more about the different ways it can be made and are also trying to obtain more precise measurements of its properties.

Please feel free to ask more top questions you have about the top quark! 😀