Particles

• Specific charge is charge divided by mass.
• Carbon-14 can be used in carbon dating which involves calculating the percentage of carbon-14 left in the object and then using the known original starting value of carbon-14 (which is the same for all living things) and its half life to calculate an age.
• The strong nuclear force acts between nucleons and counteracts the electrostatic force of attraction between protons in order to keep the nucleus stable. It is attractive at a short range between 0.5 and 3 fm but repulsive at less than 0.5 fm to stop the nucleus collapsing.
• Unstable nuclei have too many protons, neutrons or both causing the strong force to not be able to hold the nucleus together. Therefore, the nucleus will decay to become stable.
• For every type of particle, there is an antiparticle which has the same rest energy (and therefore mass) but opposite of all its other properties.
• Annihilation is where a particle and its corresponding antiparticle collide and as a result their masses are converted to energy and two photons are emitted in order to conserve momentum.
• Annihalition is used in a PET scanner, which allows 3D images of the body to be taken, aiding medical diagnosises. A positron emitting radioisotope is introduced into the patients system which annihilates with electrons, emitting gamma rays that can be detected.
• Pair production is where one photon is converted into an equal amount of matter and antimatter. The photon can only produce a particle antiparticle pair of total rest energy less than the photons energy.
• The four fundamental forces are gravity, electromagnetic, weak nuclear and strong nuclear.
• The strong force has a range of 3 x10^-15 m, acts on hadrons, and its exchange particle is a gluon.
• The weak force has a range of 1 x10^-18, acts on all particles, and its exchange particle is a boson.
• The electromagnetic force has an infinite range, acts on charged particles, and its exchange particle is a virtual photon.
• Gravity has an infinite range, acts on massive particles, and its exchange particle is a graviton.
• Exchange particles carry energy and momentum between particles experiencing a force.
• Feynman diagrams show particle interactions over time.
• In every junction in a Feynman diagram, charge must be conserved.
• Electron capture involves a W+ boson being transferred from a proton to an electron and a neutron and electron neutrino being formed.
• Electron-proton collision involves a W- boson being transferred from an electron to a proton, and a neutron and electron neutrino being formed.
• All particles are either hadrons or leptons.
• Leptons are fundamental particles that do not experience the strong force.
• Hadrons are not fundamental and do experience the strong force. They can be split into two groups: baryons, which are formed of three quarks, and mesons, which are formed of a quark and antiquark.
• The proton is the only stable baryon, and therefore all baryons will eventually decay into a proton.
• Baryon number and lepton number are always conserved in particle interactions and are 1 for a baryon/lepton, -1 for an anti baryon/lepton and 0 if not a baryon/lepton.
• A muon is a heavier version of an electron and decays into electrons.
• Strange particles are produced by the strong interaction but decay by the weak interaction. Strangeness is conserved except in weak interactions where it can also change by 1 or -1.
• Kaons decay into pions.
• There are six types of quarks: up, down, strange, top, bottom and charm.
• Up, down and strange quarks have the charge +2/3, -1/3, -1/3, the baryon number +1/3, +1/3, +1/3 and strangeness 0, 0, -1 respectively.
• The quark combinations for kaons are: k0 ds', k+ us', k- su' and pions are: pi0 uu' or dd', pi+ ud', pi- du', where ' represents an antiquark and is written in the form qq'.