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Is there no energy conservation?

  1. Apr 6, 2007 #1
    When we look at a particle's rest frame
    its energy is Mc^2.
    But the particle decay has some width, so the products of the particle,generally, will have total energy different than Mc^2.
    How can it be, is there no energy conservation?
     
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  3. Apr 6, 2007 #2

    ZapperZ

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    Did you ever look at the kinetic energy of the decay products?

    Zz.
     
  4. Apr 6, 2007 #3

    Hootenanny

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    There certainly is conservation of energy, the two decay particles may have some non-zero velocity in the original particle's rest frame. Energy and momentum are always conserved (in a closed system).

    Edit: Dammit Zz.
     
  5. Apr 6, 2007 #4
    At the beginning the two decay product did not exist.
    For instance when a rho particle decay into to pions,
    its energy in its rest frame is Mc^2.
    But the decay products, the two pions,generally will have different energy than the original rho.
    This is, as I understand, the meaning that the decay has a width.
     
  6. Apr 6, 2007 #5

    Hootenanny

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    The decay width is another name for the decay rate of a species. However, to answer what I believe your question to be; due to the HUP any particle with a finite lifetime has a non-zero mass distribution (has some uncertainty in the mass), this will result in a non-zero mass distribution for the products.
     
  7. Apr 7, 2007 #6
    What do you mean by some uncertainty in the mass, is this like uncertainty
    of the momentum?
    Is the wave function of the particle is a superposition of eigen vectores with different mass eigen value?
    Isn't the mass of the particle is the exact value that appear in the hamiltonian?
     
  8. Apr 7, 2007 #7

    ZapperZ

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    You do know that in these experiments, they don't measure just one decay, don't you? They measure a gazillion to get the statistics. So what do you think the "mass width" here means?

    Zz.
     
  9. Apr 7, 2007 #8
    First of all, I asked about the "mass width" because I don't understand this
    expression.
    Second, the fact that "They measure a gazillion to get the statistics" is gust a technical mean to learn about the physics, it is still meaningful to ask about one particle.
    When I check about the muon mass in wikipedia or in any other place I always find gust one number, I never saw the width of its mass only of its decay, but even if there is such a thing as "mass width" it must influence the hamiltonian and also the one particle wave function.
     
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