# KS5 Particle Physics

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# Particle Physics - Objectives

Content

• Constituents of the atom
• Stable and unstable nuclei
• Particles, antiparticles and photons
• Particle interactions
• Classification of particles
• Quarks and antiquarks

Learning Outcomes

Students should know:

• Simple model of the atom: Proton, neutron, electron; their charge and mass in SI units and relative units.
• Specific charge of nuclei and of ions. Atomic mass unit is not required.
• Proton number Z, nucleon number A, nuclide notation
• The meaning of isotopes and the use of isotopic data
• The strong nuclear force; its role in keeping the nucleus stable; short-range attraction to about 3 fm, very-short range repulsion below about 0.5 fm
• Equations for alpha decay and β - decay including the need for the neutrino.
• That the existence of the neutrino was hypothesised to account for the conservation of energy in beta decay
• for every type of particle, there is a corresponding antiparticle.
• the positron, the antiproton, the antineutron and the antineutrino are the antiparticles of the electron, the proton, the neutron and the neutrino respectively.
• Comparison of particle and antiparticle masses, charge and rest energy in MeV.
• Photon model of electromagnetic radiation, the Planck constant, E = hf = λ/hc
• There are four fundamental interactions: gravity, electromagnetic, weak nuclear, strong nuclear (the strong nuclear force may be referred to as the strong interaction)
• Knowledge of annihilation and pair production processes and the respective energies involved. The use of E = mc2 is not required in calculations.
• Concept of exchange particles to explain forces between elementary particles (knowledge of the gluon, Zo and graviton will not be tested).
• The electromagnetic force; virtual photons as the exchange particle.
• The weak interaction limited β - , β + decay, electron capture and electron-proton collisions; W + and W - as the exchange particles.
• Simple Feynman diagrams to represent the above reactions or interactions in terms of particles going in and out and exchange particles.
• Hadrons: baryons (proton, neutron) and antibaryons (antiproton and antineutron) and mesons (pion, kaon).
• Hadrons are subject to the strong nuclear force.
• Candidates should know that the proton is the only stable baryon into which other baryons eventually decay; the decay of the neutron should be known.
• Baryon number as a quantum number
• Conservation of baryon number
• The pion as the exchange particle of the strong nuclear force.
• The kaon as a particle that can decay into pions.
• Leptons: electron, muon, neutrino (electron and muon types).
• Leptons are subject to the weak interaction.
• Lepton number as a quantum number
• Conservation of lepton number for muon leptons and electron leptons.
• The muon as a particle that decays into an electron
• Strange particles are produced through the strong interaction and decay thorugh the weak interaction (e.g. kaons)
• Strangeness as a quantum number to reflect the fact that strange particles are always created in pairs.
• Conservation of strangeness in strong interactions.
• Strangeness can change by 0, +1, or -1 in weak interactions
• Particle physics relies on the collaborative efforts of large teams of scientists and engineers to validate new knowledge.
• Up (u), down (d) and strange (s) quarks only.
• Properties of quarks: charge, baryon number and strangeness.
• Combinations of quarks and antiquarks required for baryons (proton and neutron only), antibaryons (antiproton and antineutron only) and mesons (pion and kaon) only.
• Change of quark character in β - and β + decay.
• Application of the conservation laws for charge, baryon number, lepton number and strangeness to particle interactions. The necessary data will be provided in questions for particles outside those specified.
• Energy and momentum are conserved in interactions.