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Escape Peaks

  1. Dec 2, 2007 #1
    How do escape peaks occure?

    I mean peaks originating from a gamma ray located at the Energy value of [tex]\ E_{peak} \equiv E_{gamma}-511KeV[/tex].

    I read that an annihilation process takes place and one of the annihilation photons escapes detection.To arive at detecting an Energy of [tex]E_{peak}[/tex] the undetected annihilation photon must have had the energy of 511KeV.

    Is there any reason why the particle system before annihilation (electron/positron) had a vanishing total momentum, so that two photons of 511KeV were emitted? Why did the incident photon interact with a nucleus in a way such that the produced particle/antiparticle pair had vanishing momentum?

    I'd appreciate help.
    Last edited: Dec 3, 2007
  2. jcsd
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