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Beta+ decay question

  1. Jun 19, 2012 #1
    This has been really bugging me. Beta plus decay is when a proton emits a positron in order to convert to a neutron, thus making the element more stable. If protons are less massive than neutrons, how does that make sense? You have less mass, emit some, and end up with more? I must be missing something. Beta minus decay makes sense to me though.
    Last edited by a moderator: Jun 20, 2012
  2. jcsd
  3. Jun 19, 2012 #2


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    Staff: Mentor

    Indeed, an isolated proton cannot decay into a neutron because the mass of a proton is less than the mass of a neutron plus the mass of a positron.

    However, a proton that is part of a nucleus can decay if the mass of the original nucleus (isotope) is greater than the mass of the final nucleus (isotope) plus the mass of a positron. The energy that is "released" (that is, appears as kinetic energy of the positron, the neutrino, and the final nucleus) comes from the difference in binding energies of the two isotopes.
  4. Jun 20, 2012 #3
    Proton is form by 2 Upper quark, and 1 Down quark

    Upper quark has +2/3 Electric charge, and Down quark have -1/3 Electric charge
    so.. that's +2/3 +2/3 -1/3 is equal +3/3 or just +1 [Positive Charge]

    so when 1 Proton emit a Positron that's mean 1 Upper quark has been reform into down quark by release +3/3 Charge.. and this one is what we called a Positron

    so 1 Upper quark [+2/3] has been change into 1 Down quark [-1/3]
    that's explain why does it's emit a Positron [-3/3] but emit into 1 particle.

    after that, Neutron has 2 Down quark, and 1 Upper quark
    [+2/3 -1/3 -1/3].. is equal 0.. [No charge]

    It's that all.
    Last edited: Jun 20, 2012
  5. Jun 20, 2012 #4
    Thanks guys, really helpful. :)
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