Particle Physics

Particle Physics

1. Atomic Structure

   • Atom
     • Made up of protons, electrons and neutrons
   • Alpha Particle
     • Helium nuclei
       • 2 protons and 2 neutrons
     • +vely charged
     • Rutherford's Alpha scatterring
       • beam of alpha p's fired at a thin piece of gold foil
         • most travelled in a straight line whilst others deflected off nucleus
           • nucleus discovered
   • Nuclide notation
     • Nucleon number
       • number of protons and neutrons
     • Proton number
   • Isotopes and ions
     • Neutral atom
       • same number of protons and electrons
     • isotopes
       • same number of protons and different number of neutrons
         • neutron
           • doesn't affect chemical property
           • affects stability
     • ion
       • atom with a charge
   • specific charge
     • ratio of charge per unit mass
       • charge/mass
   • stable/unstable nuclei
     • Forces in nucleus
       • EM force
         • causes protons to repel each other
       • Gravitational force
         • all nucleons attract to each other due to mass
       • EM>>> gravitational force
       • SNF
         • Overcomes EM force
           • short range

2. Nuclear Decay

   • bigger nucleus=more unstable
     • emit particles to become more stable
   • alpha decay
     • Usually happens when there are more than 82 protons
     • the nucleus will emit an alpha particle
   • Beta-Minus decay
     • happens in isotopes that are nucleon rich
       • more neutrons than protons
     • neutron becomes proton and nucleus emits electron and anti-neutrino
     • beta particle
       • fast moving electron

3. Hypothesis of Neutrinos

   • energy of electron and nucleus after decay was < than before
     • this didn't follow rule of CONSERVATION OF ENERGY
       • Another particle that was neutral and almost zero mass

4. Photons

   • Electromagnetic spectrum
     • a continuous spectrum of all possible frequencies of EM
     • all EM waves travel at the speed of light
     • Electromagnetic Waves
       • Radiation emitted by charged particles losing energy
       • Consists of an oscillating electric wave and a magnetic wave
       • Each burst is a packet of EM waves and is referred to as a photon
   • E=hf
   • E-hc/wavelength

5. Antiparticles

   • All particles have a corresponding particle that
     • has the same mass
     • has the opposite charge
     • annihilates its particles when they collide
     • can be created along with its particle from a photon with sufficient energy
   • can be seen
     • in some radioactive isotopes
     • in high energy collisions between particles
     • in cosmic rays

6. Pair production and annihilation

   • Annihilation
     • when particle meets antiparticle
     • masses converted into energy
     • all mass + KE is converted to 2 photons of equal frequency
   • Pair production
     • energy converted into mass
     • minimum energy needed is the total rest energy of the particle produced
     • fire 2 protons with large KE at each other
     • gamma ray photon -> electron positron
       • PET scanner
         • scintillator contains scintillator crystals that produce flash of light

7. Hadrons

   • Baryons
     • nucleons
     • all unstable except free protons
     • all decay into a proton
     • protons/neutrons have a baryon number
   • Mesons
     • interact with baryons via strong force
     • all unstable
     • pion
       • any charge
       • proton>rest mass>electron
     • kaon
       • any charge
       • electron>RM>PION
   • Can feel SNF
   • made up of quarks

8. Leptons

   • fundamental particles
   • interact via weak interaction, gravitational + EM
   • muon
     • unstable lepton
     • heavy electron
     • eventually decay into electron
   • electron
     • stable lepton
   • corresponding neutrino
     • 0 charge+ mass
     • only take part in weak interactions

9. Particle Interactions

   • Particle exchange
     • virtual particles

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