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ANNIHILATION. PARTICLE PHYSICS. PARTICLE PHYSICS. e +. e -. Atom 1x10 -10 m. Nucleus 1x10 -15 m. +. n. n. +. n. n. +. U. U. Quarks 1x10 -18 m. D. ?. ?. ?. CLASSIFICATION. ALL PARTICLE, EXCEPT FOR THE GAUGE BOSONS, ARE EITHER :. LEPTONS. GREEK leptos ( leptos) =.

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  1. ANNIHILATION PARTICLE PHYSICS PARTICLE PHYSICS e+ e-

  2. Atom 1x10-10 m Nucleus 1x10-15 m + n n + n n + U U Quarks 1x10-18 m D ? ? ?

  3. CLASSIFICATION ALL PARTICLE, EXCEPT FOR THE GAUGE BOSONS, ARE EITHER : LEPTONS GREEK leptos (leptos) = LIGHT OR ROBUST OR HEAVY HADRONS GREEK hadros (hadros) = Gauge Bosons are the exchange particles which mediate the four types of interactions or forces

  4. LEPTONS HADRONS GAUGE BOSONS Electron Baryons Mesons virtual photons electron neutrino muon neutrino Electromagnetic force Muon W+ W- Z0 The weak force gluons Tau particle The strong force Tau neutrino (not fundamental) (fundamental) 3 Quarks QQQ 2 Quarks Q antiQ Proton p Pions Neutron n Kaons gravitons Gravity All leptons and hadrons have a corresponding antimatter particle

  5. Matter and Antimatter annihilate each other e.g. a collision between an electron and a positron can produce two gamma rays

  6. ANNIHILATION The two gamma rays have to travel in opposite directions so that momentum is conserved e+ e- The amount of energy released is, in line with Einstein's theory of Special Relativity [E = mc2], equivalent to E = 2 me c2, where me is the mass of the electron [and the positron] The energy of a photon of frequency,f, is given by E = hf, where h is Planck’s constant. Hence the frequency of the gamma rays is found by equating: 2mec2 = 2hf

  7. MATTER AND ANTIMATTER Corresponding Matter and Antimatter Particles have : • the same mass • opposite charges, if they are charged • opposite spin One particle is like the MIRROR IMAGE of the other The antimatter particle behaves as though it has negative energy and is travelling backwards in time, when it is compared with its matter equivalent

  8. PAIR PRODUCTION + - IN THE PRESENCE OF A MASSIVE NUCLEUS, A PHOTON CAN PRODUCE AN ELECTRON POSITRON PAIR If there is a magnetic field acting inwards, which is the positron? NUCLEUS hf= 2mec2 + EK

  9. We currently think of four main forces of nature: • electromagnetism • weak force • strong nuclear force • gravity Physicists think that all forces are caused by the exchange of particles. Imagine two jugglers playing on a frozen lake. When they start throwing their batons at each other, they will be pushed apart. The batons carry momentum from one juggler to the other. This momentum pushes each juggler away from the other across the slippery ice.

  10. Force Particles it affects Exchange particle Electro-magnetic anything with charge virtual photon Range Relative strength Weak all fundamental particles W+, W-,Z0 Strong nuclear force quarks gluon Gravity anything with mass graviton Infinite 10-2 10-18 m 10-5 10-15 m 1 Infinite 10-39 The Higgs particle or field is a kind of stuff in the vacuum causing originally zero mass particles to gain mass. In the electro-weak theory the photon (and the gluon in the quark theory) remain massless.

  11. FEYNMAN DIAGRAMS Time Space THESE ARE DIAGRAMS IN SPACE AND TIME USED TO REPRESENT VARIOUS INTERACTIONS In the interaction below 2 electrons come together, throw virtual photons at one another, thus repelling each other.

  12. e- p Time n Space Beta Minus Emission w - w -

  13. e+ n νe Time p Space Beta PLUS Emission w+ w+

  14. ve n Time p e- Space Electron Capture w+ w+

  15. p e- Time n ve Space Neutrino - Neutron Collision w+ w+

  16. e+ n Time p Space Antineutrino - Proton Collision w+ w+

  17. ve n Time p e- Space Electron - Proton Collision w- w-

  18. THREE GENERATIONS OF MATTER

  19. Quarks also have another property called “COLOUR CHARGE” [ usually referred to as just “colour” ] D D U U U D AD U The three possible colours arered,blueandgreen. Red blue and green together make white and quarks particles can only exist where the quarks altogether produce a colourless mix proton neutron π+ meson

  20. Have odd half integer spin usually sometimes CLASSIFICATION BY SPIN FERMIONS BOSONS Have integer spin Gauge Bosons [Force carriers] Mesons Leptons Quarks Baryons An atomic nucleus is either a fermion or boson depending on whether the total number nucleons is odd or even, respectively. This accounts for superconductivity and the superfluidity of Helium [ a boson ] at low temperatures

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