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Why we need intermediate particles

  1. Jan 31, 2009 #1
    why we need intermediate particles? i.e. why we want virtual particles like w,z boson etc..
    for example,in the beta minus decay..neutron is converted into proton+electron+neutrino...
    n-> p + e + ne
    then we why want something intermediate w- like this
    n-> p + w- -> p + e + ne

    both are same only..then why we want w-...

    we can write
    0 = 1 -1
    0 = 1 + a where a = -1 + 0
    both are same..we can write many equations like this..

    I am confussed ..can someone explain?
  2. jcsd
  3. Jan 31, 2009 #2


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    the physics going on is not n-> p + e + ne .. that is just counting. If you want to understand and describe why and how the neutron decays, one needs formulas which are consistent with special relativity and quantum mechanics. And then one developed quantym field theory. And in quantumm field theory, the interaction will be described by, if you do a perturbative series expansion of the S-matrix, a sum of such intermediate states with a (or several) virtual particle(s) mediating the interaction.

    You can get some introductory material on this, with math, if you PM me.
    Last edited: Jan 31, 2009
  4. Jan 31, 2009 #3
    many thanks..i PMed u..
  5. Jan 31, 2009 #4


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    The original theory of the weak interaction put forth by Fermi in the early 1930s did not include particle exchange. Even for some time after the unified electroweak theory (Weinberg-Salam) with W and Z exchange bosons appeared in the late 1960s, the Fermi theory could adequately describe accelerator experiments involving neutrinos etc., at the energies that were available then. This was the case when I was in graduate school in the 1970s. Finally in the 1980s energies increased to the point where Fermi theory and Weinberg-Salam gave measurably different predictions, and experiments supported the newer theory.
  6. Jan 31, 2009 #5


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    it was just a point interaction in Fermi theory, and indeed many weak decays can be well approximated as Fermi decay, such as muon decay.

    But I think OP was after the more general stuff, in any process, why need for virtual particles.
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