Pair Annihilation and Production

Pair Annihilation and ProductionPhysical and Applicative Overview

Joey GoodknightPhysics 129October 21, 20101e+/e-Getting and Getting Rid of Them2GoalsBasic Physical MechanismsAntimatter is EverywhereToo Many Electrons!3History, Motivation and MechanismsHow and Why the Positron?4Antimatter: The Publics View5Reality Check1 gram of anti-p+2 X 1014 Joules4 Little Boys (Hiroshima)2 Fat Mans (Nagasaki)$25,000,000,000.00 (2009 Nasa Study)~GDP of YemenAdmittedly only 1/20 of US defense Spending~Yearly Nuclear Weapons Spending (1998 ) Containment Unrealistic past 1012 atomsFrom Space: Classic Doomsday TheoryTungaska Event

6Sorry, Back to e+/e-7Pair Production?EM Phenomenon3 main methods: e+ + e- + e+ + e-DecayOther Possibilities?

8ConditionsE ConservationE=h=~mec2~1 femtometer ~1023 Hz Well past gamma raysP ConservationRestricts DiagramsLeast ExpectedFemtosecond 800nm focus

9Pair Annihilation?matter+anti-matterNothingMuch simpler than Prod.P ConservationPositroniumBound stateL=0, annihilation!

10History: First Pair ProductionDirac1929Carl Anderson1932 under MillikanCloud Chamber Tracks 208Tl1936 Nobel

11Nifty ApplicationsTheyre All Around Us!12What if qeqe?13+q-q+qGoop, full of dipoles14+q-q

E=?E=?15Vacuum PolarizabilityVacuum PhotonsCreate Virtual PairsShield ChargeVacuumDielectricQED Triumphspin1997 Confirmation

16Positron Emission TomographySeein inside you17Positron (+) DecayWeak Force Decay11C, 40K, 13N, 18F etc.

18PET: How it Works

e+

e-

Photons Come out at 180 degrees to each otherComplex ProcessingDensity Map of Tracer19PALSAlways a Friend of Solid State Physicists20e+Positron SourceNa, usuallyScan MaterialCorrelate emission with annihilationGenerate map of open volume defectsGets trappedLive longerDefects are what make many semiconductors cool21Hawking Radiation22

Black hole, kicks 23Thank You24