Particles

• Particle groups


  • Hadrons
  • Leptons
• Leptons


  Fundamental particles including electron, muon, and neutrino
• Lepton number


  1 for leptons, -1 for antiparticles
• Types of neutrinos


  • Electron neutrinos
  • Muon neutrinos
• Quark flavours


  • Up
  • Down
  • Strange
• Baryons


  • Neutron (up down down)
  • Proton (up up down)
• Electromagnetic force


  Affects charged particles, exchange particle is photon
• Weak force


  Affects any particle, exchange particles are W+, W-, Z0 bosons
• Strong force


  Affects hadrons, exchange particle is gluon
• Electrostatic repulsion and strong force in nucleus


  Balanced to make stable nucleus
• Strong force range


  1. 4 fm, switches from attractive to repulsive at 0.5 fm
• In any interaction, charge, baryon number, and lepton number must be conserved
• Feynman diagrams


  Represent interactions, always weak interaction with W+ or W-
• In beta minus decay, a down quark in the neutron decays to an up quark, turning it into a proton
• Strangeness rules


  • Interactions with leptons are weak
  • Interactions with hadrons and conserved strangeness are strong
  • Interactions with hadrons and non-conserved strangeness are weak
• Charge to mass ratio

  Charge in coulombs divided by mass in kg
• Radiation is any particle or wave emitted by something
• Gamma radiation is emitted by the nucleus of an atom
• Gamma radiation can ionize atoms and cause damage to cells
• Alpha decay


  1. Nucleus emits 2 protons and 2 neutrons (alpha particle)

  2. Daughter nucleus has lower atomic number
• Beta decay


  1. Neutron turns into proton, electron, and antineutrino

  2. Atomic number increases by 1, mass number unchanged
• Particle-antiparticle annihilation produces 2 photons
• Minimum energy/frequency of annihilation photons

  Equal to 2mc^2 or 2hf
• Pair production


  Photon with sufficient energy converts into particle-antiparticle pair
• Electron energy levels in atoms

  Discrete levels, with ground state as lowest
• Electron excitation and de-excitation

  1. Electron can absorb photon to reach higher level

  2. Electron falls back down, emitting photon(s)
• Ionization energy


  Minimum energy to remove electron from atom