# Particle Physics

### The following table is my interpretation of the main families of known sub-atomic particles.

Sub-atomic particles
Even spin
Bosons
Odd spin
Fermions
LightForce carriers
e.g. photon
Leptons
e.g. electron
(experience the
weak nuclear force)
Heavy
(generally)
(experience the
strong nuclear force)
Mesons
Made of two quarks
Baryons
Made of three quarks
e.g. proton, neutron
Quarks

### The following table gives more detail on members of these families.

• Mass is given in Gev/c2 , which is a Giga-Electron-Volts divided by the speed of light squared.
• Electon-Volts is a measure of energy, and is the energy gained by an electron crossing a potential of one volt.
• 1eV = 1.6 x 10 -19 joules.
• So 1GeV = 1.6 x 10 -10 joules
Mass is measured in terms of energy because they are equivalent according to Einstein's equation E = mc2.
1GeV is about the amount of energy required to create a proton, because the mass of a proton is 0.938GeV/c2 = 1.67 x 10-27 kg.
• Electric charge is given in terms of the charge of a proton, which is +1. This is equivalent to 1.6 x 10-19 coulombs
• Spin is the internal angular momentum of a particle. It is given by h/2pi where h is Planck's constant.
This is 6.58*10 -25 GeV s = 1.05*10 -34 J s
Fermions
(Sub-atomic particles which are constituents of matter
with an odd number of half-spin units, i.e. 1/2, 3/2 5/2, ...)
Leptons (spin=1/2) Quarks (spin = 1/2)
ClassName Mass (GeV/c2)Electric charge Name (Flavor) Approx. Mass (GeV/c2) Electric charge
I electron 0.000511 -1 up 0.005 +2/3
electron-neutrino < 7x10-9 0 down 0.01 -1/3
II muon 0.106 -1 strange 0.2 -1/3
muon-neutrino < 0.0003 0 charmed 1.5 +2/3
III tau 1.7771 -1 top 170 +2/3
tauon-neutrino < 0.03 0 bottom 4.7 -1/3
Bosons
(Sub-atomic particles which are force carriers
with an even number of half-spin units, i.e. 0, 1, 2, ...)
Unified electroweak force (spin=1) Strong/Color force (spin = 1)
Name Mass (GeV/c2) Electric charge Name Mass (GeV/c2) Electric charge
Photon 0 0 Gluon 0 0
W - 80.22 -1
W + 80.22 +1 Gravity force (spin = 2)
Z 0 1.187 0 Graviton 0 0
(Sub-atomic particles which are heavy, strongly interacting, and made of quarks)
Baryons (qqq) and Antibaryons (q-q-q-)
are made up of three quarks, so have odd spin
Name Mass (GeV/c2) Electric chargeQuark content Spin Lifetime (secs)
Proton 0.93828 +1uud 1/2 > 1039
Neutron 0.93957 0 udd 1/2 898
lambda 1.1156 0 uds 1/2 2.6 x 10 -10
omega 1.6725 -1sss 3/2 0.8 x 10 -10
Mesons (qq-)
are made up of a quark and antiquark, so have even spin and are therefore bosons
Name Mass (GeV/c2) Electric chargeQuark content Spin Lifetime (secs)
Pion 0.13957 +1ud- 0 2.6x10 -8
Kaon 0.49367 -1su- 0 1.2x10 -16
Rho 0.770 +1ud- 1
D+1.869 +1cd- 0
Eta-c 2.979 0 cc- 0

Subatomic particles

• There are many, but only a very small number are stable, and therefore only these make up the world.
• Unstable subatomic particles are mostly known from high-energy experiments, where they very quickly decay into stable particles.
• Electric charge only comes in whole units (except for quarks)
• Spin come in half-units.
• An antiparticle has the opposite charge, but the same mass and spin, as its pair.
• All matter consists of atoms.
• An atom consists of a nucleus with a number of “orbiting” electrons.
• An atom is about 10 -8cm
• The nucleus is 10 -12cm diameter, so is a ten-thousanth of the size of the whole atom.
• The nucleus of an atom consists of protons and neutrons.
• Electrons are bound to the nucleus by electromagnetic force.
• Protons and neutrons are held together by the “strong nuclear force”.
• The strong nuclear force is carried by pions (originally called mesons).
• When a pion decays, it forms a muon (among other things)
• A muon is the same as an electron, but 206 times heavier.
• A muon is unstable, and decays into electrons in 2 microseconds.
• Neutrinos are another member of the family of light, weakly-interacting particles called leptons.
• Leptons feel the “weak nuclear force”.
• The charged leptons also are subject to the electromagnetic force.
• Quarks have a charge of either one-third or two-thirds of a unit, so can only exist in pairs or triples.
• Six types of quark are known, up/down, strange/charmed and top/bottom.
• Quarks feel the strong nuclear force.
• All matter is made of up/down quarks plus electrons.
• Further levels, as in the diagram, are equivalent to the first, but heavier, and mostly unstable.

Questions:

• Are all bosons force carriers?

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