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The antineutrino in Beta decay

  1. Dec 29, 2008 #1
    I understand the physical changes in beta decay that eventually lead to the virtual particle, a W- boson being formed. However I do not understand the physical changes that take place, which eventually lead to an antineutrino being emitted. What changes take place in the W- boson, that make it decay into an antineutrino and electron?

    I would also be glad if someone could explain why the physical changes take place?

    Thanks in advance
    - Adam
  2. jcsd
  3. Dec 29, 2008 #2

    Vanadium 50

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    I'm not sure that I understand what you mean. Also, you do understand that "a virtual particle being formed" is sort of a contradiction. The particle is virtual, not real. It's not formed.
  4. Dec 29, 2008 #3
    By this do you mean that the antineutrino isn't really there after beta decay?
    If the production of an antineutrino is virtual, then would you be able to explain how?

    Simply, I would like to understand why we have an antineutrino involved ,regardless of it being real or virtual.

    Thanks for attempting the answer the question.
  5. Dec 29, 2008 #4

    Vanadium 50

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    There is an antineutrino around to conserve spin (and other quantum numbers, like lepton number). If I have the decay [tex]n \rightarrow p + e^- + \overline{\nu}[/tex], I have a spin-1/2 object on the left hand side and without the neutrino, I have either a spin-0 or spin-1 ensemble on the right. I also have L = 0 on the left and L = 1 on the right. Finally, the energy spectrum of the electron is characteristic of three-body decays, not two body decays. For all of these reasons, one expects an additional particle produced, the antineutrino.

    Of course, today those (anti-)neutrinos have been measured.
  6. Dec 29, 2008 #5
    This has made me understand why it is necessary to produce an anti-neutrino in beta decay. So what are the spin and lepton values for the neutrino which help to create a balances on both sides of the decay?

    Thank you for your time,
  7. Dec 29, 2008 #6


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    The neutrino is a spin 1/2 particle and a neutrino has lepton number +1 and an antineutrino has -1.
  8. Dec 29, 2008 #7
    Thanks for this. I now understand how the anti-neutrino helps to balance things out.
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