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Electron Polarization

  1. May 4, 2013 #1
    ¿ Why the photons emitted by an electron are desintegrated in a photon, and then in an electron a positron?

    The positive charge stay near the electron doing that charge stay minus than its real value. But, ¿ why don´t matter the same with the mass??
     
  2. jcsd
  3. May 4, 2013 #2

    mfb

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    At least for me, it is hard to guess what you are asking.

    Do you think of electromagnetic showers and pair production here? If high-energetic electrons come close to a nucleus, they can emit high-energetic photons.
    If high-energetic photons come close to a nucleus, they can produce an electron and a positron. It is possible to describe those processes with quantum field theory, but physics cannot answer "why" on a fundamental level. We can just observe the universe, and make theories to match those observations.

    I don't understand that.
     
  4. May 4, 2013 #3
    E=mc^2, energy-mass equivalence does balance before and after the pair-production.
     
  5. May 4, 2013 #4
    About the questions, I ask the question in the frame of QFT, of course. On respect the second question, well, if all positrons stays near the electron, same you must measure a minor charge because you are really measuring the positron masses with the electron mass, a bigger mass ( the electron mass and all the positron masses) must be measured too. But the second affirmation is not certain.
     
  6. May 4, 2013 #5

    mfb

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    Why should positrons stay near some electrons?
    They can form positronium (bound state of electron+positron), but that is rare in high-energetic collisions.
    Where do you measure which charge how?
    Charge measurements and mass measurement are different.
     
  7. May 4, 2013 #6
    Of course, they are different. But no relation with my question
     
  8. May 4, 2013 #7

    mfb

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    I don't understand your question then.

    Positron measurements are done on positrons alone, without electrons.
     
  9. May 5, 2013 #8
    No, the shielded charge we measure is the charge of electron+ positrons cloud, but if we measure the mass of electron+positrons cloud, the result wolud be bigger . Why in the charge case the measurement is joint and in mass case is disjoint?
    __________________

    Ok, I take care now. The gravitational force is negligible at this scales. Thanks anyway.
     
    Last edited: May 5, 2013
  10. May 5, 2013 #9

    mfb

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    Ah now I think I get it. you mean loop corrections?
    Those are not "electrons close to positrons" or whatever - those loops are not real particles. They are a model to describe how QFT gives particles; the bare mass is some number that influences the "particle mass", those two are not the same.
     
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