Particle physics

• Proton

  Charge: +1.6x10^-19

  Mass: 1.67x10^-27

  Specific charge: 9.58x10^7
• Neutron

  Charge: 0 Mass: 1.67x10^-27

  Specific charge: 0
• Electron

  Charge: -1.6x10^-19

  Mass: 9.11x10^-31

  Specific charge: 1.76x10^11
• Specific charge

  charge / mass
• Isotopes

  atoms with the same number of protons but different number of neutrons
• Strong nuclear force

  keeps nuclei stable by counteracting the electrostatic force of repulsion between protons in the nucleus.

  • only acts of nucleons
  • short range (attractive up to separations of 3fm but repulsive below separators of 0.5fm)
• Shape of graph for SNF

  shape:

  
• Unstable nuclei

  have too many protons or neutrons or both.

  in this case, the SNF is able to keep them stable
• Decay

  the type of decay will depend on the amount of protons and neutrons there are
• when does alpha decay occur?

  When there are too many of both protons and neutrons
• alpha decay

  Proton number decreases by 2

  Nucleon number decreases by 4
• alpha decay equation

  .

  
• beta minus decay occurs when...

  occurs when nuclei are neutron rich
• beta minus decay

  proton number increases by 1

  nucleon number stays the same
• beta minus decay equation

  .

  
• anitparticles

  For every particle there is an anitparticle which has the same rest energy and mass but all other properties are opposite
• antiparticle pairs

  electron and positron

  electron neutrino and electron antineutrino
• Electromagnetic radiation

  travels in packets called photons

  These transfer energy and have no mass
• Photons

  energy of photons is directly proportional to the frequency of electromagnetic radiation.

  Equation: E = hf = hc/wavelength
• h

  is Planck's constant = 6.63 x 10^-34
• Annihilation

  occurs when a particle and it's corresponding antiparticle collide and as a result their masses are converted into energy.
• what happens to photons in annihilation?

  the energy released from annihilation is released in the form of 2 photons moving (because they have kinetic energy) in the opposite directions (in order to conserve momentum)
• example of application of annihilation

  PET scanner which allows 3D images of inside the body to be taken making medical diagnoses easier.

  done by introducing a positron-emitting radioisotope into the patient, and when positrons are released, they annihilate with electrons in the patient's system which will emit gamma photons which are easily detected
• Pair production

  a photon converted into an equal amount of matter and antimatter
• when can pair production occur?

  When the photon has energy greater than the total rest mass of both particles
• What happens to excess energy in pair production?

  Converted into kinetic energy
• What are the 4 fundamental forces?

  Gravity

  Electromagnetic

  Weak nuclear

  Strong nuclear
• Forces between particles are caused by exchange particles
• Exchange particles

  Carry energy and momentum between the particles experiencing the force.
• Strong interaction

  exchange particles: Gluon

  range /m: 3x10^-15

  acts on: Hadrons
• Weak interaction

  exchange particles: W boson (+ and -) range /m: 10^-18 acts on: All particles
• electromagnetic interaction

  exchange particles: virtual photon

  range /m: infinite

  acts on: charged particles
• gravity

  exchange particles: Graviton

  range /m: infinite

  acts on: particles with mass
• Weak nuclear force

  responsible for beta decay, electron capture and electron-proton collisions
• electron capture

  p + e- --> n + electron neutrino using W+ boson
• electron-proton collision

  p + e- --> n + electron neutrino using W- boson
• Classification of particles

  All particles are either hadrons or leptons
• Leptons

  Leptons are fundamental particles meaning they can not be broken down any further. They do not experience the strong nuclear force.
• Hadrons

  hadrons are formed from quarks and they do experience the strong force
• quarks

  are fundamental particles