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Pair Annihilation and Production

Pair Annihilation and Production. Physical and Applicative Overview. Joey Goodknight Physics 129 October 21, 2010. e + /e -. Getting and Getting Rid of Them. Goals. Basic Physical Mechanisms Antimatter is Everywhere Too Many Electrons!. History, Motivation and Mechanisms.

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Pair Annihilation and Production

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  1. Pair Annihilation and Production Physical and Applicative Overview Joey Goodknight Physics 129 October 21, 2010

  2. e+/e- Getting and Getting Rid of Them

  3. Goals Basic Physical Mechanisms Antimatter is Everywhere Too Many Electrons!

  4. History, Motivation and Mechanisms How and Why the Positron?

  5. Antimatter: The Public’s View

  6. Reality Check • 1 gram of anti-p+ • 2 X 1014 Joules • 4 “Little Boy”s (Hiroshima) • 2 “Fat Man”s (Nagasaki) • $25,000,000,000.00 (2009 Nasa Study) • ~GDP of Yemen • Admittedly only 1/20 of US defense Spending • ~Yearly Nuclear Weapons Spending (1998 ) • Containment Unrealistic past 1012 atoms • From Space: Classic “Doomsday Theory” • Tungaska Event

  7. Sorry, Back to e+/e-…

  8. Pair Production? • EM Phenomenon • 3 main methods: • γ  e+ + e- • γ + γ  e+ + e- • Decay • Other Possibilities?

  9. Conditions • E Conservation • E=hυ=~mec2 • λ~1 femtometer • υ ~1023 Hz • Well past gamma rays • P Conservation • Restricts Diagrams • Least Expected • Femtosecond 800nm focus

  10. Pair Annihilation? • matter+anti-matter • “Nothing” • Much simpler than Prod. • P Conservation • Positronium • Bound state • L=0, annihilation!

  11. History: First Pair Production • Dirac • 1929 • Carl Anderson • 1932 under Millikan • Cloud Chamber Tracks • γ 208Tl • 1936 Nobel

  12. Nifty Applications They’re All Around Us!

  13. What if qe≠qe?

  14. +q’ -q’ +q Goop, full of dipoles

  15. E=? E=? -q +q

  16. Vacuum Polarizability • Vacuum Photons • Create Virtual Pairs • Shield Charge • VacuumDielectric • QED Triumph • spin • 1997 Confirmation

  17. Positron Emission Tomography Seein’ inside you

  18. Positron (ß+) Decay Weak Force Decay 11C, 40K, 13N, 18F etc.

  19. PET: How it Works • Photons Come out at 180 degrees to each other • Complex Processing • Density Map of Tracer γ e- e+ γ

  20. PALS Always a Friend of Solid State Physicists

  21. γ γ Positron Source Na, usually e+ • Scan Material • Correlate emission with annihilation • Generate map of open volume defects • Gets trapped • Live longer • Defects are what make many semiconductors cool γ

  22. Hawking Radiation

  23. Thank You

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