Particle Physics

Particle Physics

1. 1 - Constituents of the Atom

   • -Proton and Neutron Mass: 1.67x10^-27 kg -Electron Mass: 9.11x10^-31 kg -Proton Charge: +1.6x10^-19 C -Electron Charge: -1.6x10^-19 C
   • Ion - Atom which has lost or gained electron to become charged. Isotope - Atoms with the same number of protons but a different number of neutrons
   • Specific Charge (or charge-to-mass ratio) is a property that can be described for any charged particle. Specific Charge (kg^-1) = Charge (C)/Mass (Kg)

2. 2 - Stable and Unstable Nuclei

   • An atomic nucleus is typically 0.1 nano-meters (1 nm = 10^-9 m). Stable nuclei are held together by the strong nuclear force.
   • The Strong Nuclear Force: Between 0 fm and 0.5 fm - Repulsive, Between 0.5 fm and 3 fm - Attractive, After 3 fm - Negledgable
   • Gamma is emitted from a nucleus in an 'excited state', typically just after alpha or beta decay. It doesn't have any affect on A or Z.

3. 3 - Particles, Antiparticles and Photons

   • All particles have a corresponding antiparticle. They have the same mass but opposite baryon numbers, lepton numbers, charges and strangeness.
   • Only particles with a charge are affected by the electromagnetic force.
   • EM radiation exhibits both WAVE and PARTICLE properties.
   • Photons have no mass, are the exchange particles for the EM force and travel at the speed of light in a vacuum. Their speed is related to their frequency and wavelength as shown by c = fλ.
   • Energy (E) is proportional to frequency (f). Proportional relationships can be made equal relationships by using a constant. In E = hf, 'h' is the Planck constant (6.63x10^-34).
   • When a particle and its antiparticle come into contact, they will annihalate each other, converting all their mass into energy.
   • A high energy photon can sometimes create a particle-antiparticle pair. This is pair production.

4. 4 - Particle Interactions

   • EM exchange particle: Photon, SNF exchange particle: Pion, WNF exchange particles: W and Z bosons.

5. 5 - Classification of Particles

   • Only hadrons experience the strong nuclear force. Hadrons include baryons (3 quarks) and mesons (quark-antiquark pair).
   • All baryons (with the exception of the proton) are unstable which means they will all eventually decay into the proton.
   • Leptons experience the weak interaction but not the strong interaction, They are divided into 3 families (electron, muon and tau). They include the respective neutrinos.

6. 6 - Quarks and Antiquarks

   • Only the weak interaction can change the flavour of a quark.
   • Energy, momentum, charge, baryon and lepton numbers are ALWAYS conserved.
   • Strangeness is only conserved in a weak interaction.
   • Particles containing strange quarks tend to have a slightly longer lifetime than similar particles without strange quarks.

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