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Particle Physics: Option Question Leaving cert Physics

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- 1. Introduction to Particle Physics
- 2. What are the Elementary Constituents of Matter? Particle Physicists Aim to answer What are the forces that control their behaviour at the most basic level?
- 3. History of Constituents of Matter AD
- 4. Conservation of energy and momentum in nuclear reactions
- 5. <ul><li>In Nuclear Reactions momentum and mass-energy is conserved – for a closed system the total momentum and energy of the particles present after the reaction is equal to the total momentum and energy of the particles before the reaction </li></ul><ul><li>In the case where an alpha particle is released from an unstable nucleus the momentum of the alpha particle and the new nucleus is the same as the momentum of the original unstable nucleus </li></ul>Conservation Laws
- 6. Neutrino must be present to account for conservation of energy and momentum <ul><li>Large variations in the emission velocities of the particle seemed to indicate that both energy and momentum were not conserved. </li></ul><ul><li>This led to the proposal by Wolfgang Pauli of another particle, the neutrino, being emitted in decay to carry away the missing mass and momentum. </li></ul><ul><li>The neutrino (little neutral one) was discovered in 1956. </li></ul>Wolfgang Pauli __
- 7. Calculate the energy released in the reaction 1.008665 u 1.007825 u 0.0005486 u 1 u = 1 J = __ kg eV
- 8. Mass difference Calculation kg kg u
- 9. It has been found by experiment that the emitted beta particle has less energy than 0.272 MeV Neutrino accounts for the ‘missing’ energy Calculation J J eV MeV
- 10. Acceleration of protons
- 11. The Cockcroft and Walton Apparatus + +
- 12. <ul><li>First artificial splitting of nucleus </li></ul><ul><li>First transmutation using artificially accelerated particles </li></ul><ul><li>First experimental verification of E = mc 2 </li></ul><ul><li>Irish Nobel Prize </li></ul><ul><li>E.T.S. Walton 1951 </li></ul>Cockroft and Walton Ernest Walton John Cockcroft
- 13. Converting mass into other forms of energy
- 14. Proton + Lithium Two alpha particles + Energy The Cockcroft and Walton Equation 1 MeV 17.3 MeV E xperimental verification of E = mc 2
- 15. Converting other forms of energy into mass
- 16. History of search for basic building blocks of nature <ul><li>Ancient Greeks: </li></ul><ul><li>Earth, Air, Fire, Wate r </li></ul><ul><li>By 1900, nearly 100 elements </li></ul><ul><li>By 1936, back to three particles: proton, neutron, electron </li></ul>
- 18. CERN LEP APPLET http://www.hep.ucl.ac.uk/masterclass/Acc_sim2/simulator.html
- 19. Proton-Proton Collisions inside the LHC at CERN
- 20. Fundamental forces
- 21. The Four Fundamental Forces
- 23. Families of particles
- 24. Mass of particles comes from energy of the reaction The larger the energy the greater the variety of particles Particle zoo
- 25. Particle Zoo
- 26. Thomson (1897): Discovers electron
- 27. Leptons Indivisible point objects Not subject to the strong force produced in radioactive decay Q = -1e almost all trapped in atoms Q= 0 all freely moving through universe _
- 28. Baryons Mesons Subject to all forces mass between electron and proton e.g. protons, neutrons and heavier particles Composed of three quarks Composed of quark-antiquark pair Subject to all forces
- 29. Antimatter
- 30. J ust as the equation x 2 =4 can have two possible solutions (x=2 OR x=-2), so Dirac's equation could have two solutions, one for an electron with positive energy, and one for an electron with negative energy. Dirac interpreted this to mean that for every particle that exists there is a corresponding antiparticle, exactly matching the particle but with opposite charge. For the electron, for instance, there should be an "antielectron" called the positron identical in every way but with a positive electric charge.
- 31. History of Antimatter 1928 Dirac predicted existence of antimatter 1932 antielectrons (positrons) found in conversion of energy into matter 1995 antihydrogen consisting of antiprotons and positrons produced at CERN In principle an antiworld can be built from antimatter Produced only in accelerators and in cosmic rays
- 32. Pair Production
- 33. Annihilation
- 34. Quark model
- 35. Quarks Fundamental building block of baryons and mesons
- 36. Three Quarks for Muster Mark Naming of Quark James Joyce Murray Gell-Mann
- 37. The six quarks
- 39. Quark Applet This applet helps identify the nature and charge of a particle given a combination of quarks http://lectureonline.cl.msu.edu/~mmp/applist/q/q.htm

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