-- NigelWatson - 13 Sep 2010


A very good explanation of this section can be found at the Particle adventure

Here are some brief details of different types of particle mentioned throughout this web-site.

Antiparticles are particles corresponding to particles we know about currently and have the same mass as that particle but have the opposite charge. When antiparticles meet their corresponding particles they annihilate each other to form two photons.

Positrons these are identical particles to electrons, having the same characteristics. The only difference being that they are positively charged. This is an example of antimatter, and releases gamma radiation when it collides with matter.

Quarks One of the fundamental constituents which make up matter. To give an example:

It is well known that an atom consists of neutrons, protons and electrons. If you could probe to see inside a proton or a neutron, you would find that each contained three smaller, constituent particles called quarks.

There are six quarks, each with its own flavour which can be simplified to a type of quark. These are: up (u), down (d), strange (s), charm (c), bottom (b) and top (t).
Particles with half integer 'spin' (angular momentum) are called fermions and consist of three quarks.
Particles with integer spin 'spin' are called bosons and consist of quark-antiquark pairs.
For example, the proton is made of two u quarks and one d quark, the neutron consists of two d quarks and one u quark. The positively charged pion consists of one u quark and one anti-d quark.

The proton, neutron, and pion are by no means the only particles which are made of quarks. All strongly interacting particles, known as baryons or mesons, are made of quarks.

Hadrons are particles that are made up of different quark/anti-quark (esentially a quark but with the opposite charge to its counterpart) combinations and interact through the strong force.

Baryons are particles made up of 3 quarks examples include the proton (p) and the neutron (n).

Mesons are particles made up of a quark and an anti-quark. Examples of mesons are the Kaon , Pion , Psi particles.

Leptons there are three types of charged lepton: the electron, muon and tau, each of which has an associated neutrino (electron neutrino, muon neutrino, tau neutrino). For each lepton there is a corresponding antiparticle (positron, anti-muon and anti-tau). Each of these also has a corresponding anti neutrino.

Neutrino - Italian for "little neutral one"- these are very low mass particles which have no charge. There are many, many billions of neutrino's passing through your little finger's nail every second, and their main source is thought to be from the Sun. They are so unreactive, that if they were to travel through a light year worth of lead, there would only be 50% change that it would hit anything along the way. Much experimental work is currently being done to understand the mass and related properties of the neutrinos. The neutrino has a very, very small mass and may constitute the source of some of the so called 'Dark Matter' present in the universe.

Topic revision: r7 - 27 Sep 2010 - 15:43:20 - NigelWatson
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