All subatomic particles, such as nucleons or electrons, and the particles they release when undergoing
processes such as radioactive decay, are organized into classes.
All particles that obey the Pauli Exclusion Principle (no two particless can have the same four
quantum numbers in a system, such as an atom) are called fermions because the Fermi-Dirac statistics
apply to them. All particles that don't obey the principle are called bosons because the Bose-Einstein
statistics apply to them.
Fermions have half-integral spin (intrinsic angular momentum). They are deemed anitsocial particles
because they obey the exculsion principle, meaning that no two fermion with the same spin can be
found in a system. The antiparticles for fermions have the same mass but opposite charge
and magnetic moment as the corresponding particle.
The first type of fermion is the baryon. They are those particles that experience the strong
nuclear force. They consist of three quarks (quark triplet).
The most notable baryons are the nucleons, the two states of which are protons
and neutrons, the particles that make up the nucleus. Other, heavier baryons, called hyperons
also exist, but they are unstable, and usually decays to a form of nucleon(heavier baryons
include the sigma, the lamda and the delta particles). Since all baryons
decay to the nucleon form, the nucleons are known as the baryon ground state.
All baryons obey the law of baryon family numbers (the family number is +1 for particles
such as protons and -1 for antiparticles such as antiprotons), which states that the sum
of the family number of all reactants in an interaction is equal to the sum of the
family number of all products. This means that, for every particle created or destroyed,
a corresponding antiparticle is also created or destroyed. For example, a proton colliding
with an antiproton will result in the mutual destruction of both particles, or, a proton
and an antiproton can be created simultaneously.
Leptons are fermions that do not experience the strong nuclear force. They are only weakly interactive,
and can be created by nuclear decay. Leptons include such particles as electrons, muons, neutrinos
and the tau particle. So, for example, an electron and a neutrino can be created by the decay
of an unstable neutron to a proton. As fermions they obey the exclusion principle, so no two electrons
can occupy the same energy level and orbital of an atom (a system) and have the same spin.
Leptons are the lightest fermions.
There are three separate laws concerning the conservation of lepton family numbers (the family numbers for leptons,
like for baryons, is +1 for particles and -1 for antiparticles), for the electrons, muons and taus.
Bosons are particles that, unlike the fermions, do not obey the exclusion principle. Generally,
fermions are particles that compose atomic structure but bosons carry out the interaction (forces)
between fermions. Bosons have integral spin and are deemed social because many bosons
can by placed in the same system in the same energy state at once.
Mesons are a class of bosons whose mass falls between the lighter lepton fermions and the heavier
baryon fermions. They consist of two quarks (quark pair), and include such particles as the p meson (pion) and the K meson (kaon). It was previously thought that the muon was a type of meson (m meson) because of its large mass (about 200 times that of the electron), but the behaviour of the
muon doesn't fit into the description of mesons, so it was reclassified.
The pion is accountable for carrying out the strong nuclear force, which is the force that
holdes the nucleus together, despite trememndous electric repulsion.
Other bosons include the W and Z particles are responsible for carrying out the weak nuclear
force and wjocj are about 200 heavier than the proton, and the photon, the particle form of light.
The photon is its own antiparticple, as is the neutral pion.