Types of Particle

Below are some very brief details of different types of particle mentioned throughout this web-site. Although this is by no means a definitive description of each of the particles, it should serve as a basic outline to those unfamiliar with any of the particles which they may come across throughout this site. Further details can be found in any good particle physics text book or web-site.


Baryons are particles made up of 3 quarks (see below)

Examples include the proton (p), neutron (n)

Kaon (K)

Kaons are mesons (see below)


There are three types of charged lepton: the electron, muon and tau particle. Each of which has an associated neutrino: the electron neutrino, the muon neutrino and the tau neutrino. Moreover for each lepton there is an antiparticle, the positron, the anti-muon and anti-tau. Each of these has associated with it an antineutrino. The properties of each are summarised below:

electron e 0.511 MeV -1 1/2
electron neutrino ne 0 MeV 0 1/2
muon m 105.7 MeV -1 1/2
muon neutrino nm 0 Mev 0 1/2
tau t 1784 MeV -1 1/2
tau neutrino nt 0 MeV 0 1/2


Mesons are particles made up of a quark (see below) and an anti-quark (which is essentially a quark but with opposite charge)

Examples of mesons are the Kaon , Pion , Psi particles


Muons are leptons. They have a charge of -1 (electron charge). The muon is 200 times more massive than the electron. Most of the particles detected by the spark chamber are muons, as they are very penetrating, and have a long lifetime.


These are massless* particles, which have no charge. There are many, many millions of neutrino's in the atmosphere. Their main source is thought to be from the Sun.

*Much experimental work is currently being done to determine if the neutrino is in fact massless. It is suspected that the neutrino may have a very, very small mass, which when added up over all the neutrinos in the atmosphere, could amount to a large amount of mass. This may constitute the source of some of the so called 'Dark Matter' present in the universe.


Also known as pi-meson. The pion is an elementary particle classified as a meson. The pion can be positively , negatively or neutrally charged. The Charged pions decay into muons and neutrinos. The neutral pions convert directly into photons:


These are identical particles to electrons, having the same characteristics. The only difference being that they are positively charged


One of the fundamental constituents which make up matter. Perhaps it is best to give an example:

It is well known that an atom is thought to be made up of neutrons, protons and electrons. If you could probe to see what a proton or a neutron consisted of, you would find that each were made up of three smaller, constituent particles called quarks.

There are six quarks (each with its own flavour) which are known to exist: up (u), down (d), strange (s), charm (c), bottom (b) and top (t).

In general particles with half integer spin (Fermions) are made up of three quarks, particles with integer spin (Bosons) are made up of quark-antiquary pairs. For example, the proton is made of a two u quarks and one d quark, the neutron consists of two d quarks and 1 u quark. The positively charged pion consists of a u quark and an 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.

What a Spark Chamber Detects

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