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Beta Decay

by MarsGhost
Tags: beta, decay
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MarsGhost
#1
Jul10-05, 08:12 PM
P: 8
One up and two downs are sitting in an unstable atom which will decay through Beta radiation. It decides to decay. One down is transformed into an up through the release of the W- particle, which decays into an electron. Basics.

What's the explanation of W+/e+ decay? Given set conditions, could an up or down indefinately release electrons and positrons? Or is the mechanism completely different?
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#2
Jul10-05, 08:35 PM
P: 30
what's more interesting is when a neutron decays into a proton, releasing the W- boson which creates the electron and anti-neutrino, where does the creation of the electromagnetic field that the proton will have come into a feynmann diagram.

I mean a neutron has no electromagnetic field, but it still has 3 quarks (ddu) where the proton has (uud) however this comination, spin, quantum numbers has the ability to give the particle an EM field. So there must be some sort of particle field (possibly photons) which are created through beta decay of a neutron to a proton.
danAlwyn
#3
Jul10-05, 08:52 PM
P: 33
To answer the OP, protons are considered to be almost completely stable. There are, however, some cases where atoms experience positron emission, and a proton changes into a neutron by emitting a positron and the accompanying neutrino. They are fairly rare though, and I think it has to do with the peculiarities of the atomic structure, something I know very little about. Carbon-11 apparently sometimes may undergo this process. It only happens because the system is unstable with the number of protons currently available, and this makes an electroweak decay of a proton into a neutron somehow favorable.

On its own, a proton is ridiculously stable. Theory suggests that it may decay into a positron and a pion (the pion then dissolving into photons), but this has yet to be observed. Due to the searches carried out so far, the lower bound on the half-life of that particular decay is [tex]10^{36}[/tex] years.

You'll have to find someone who knows more to get a better answer.

James R
#4
Jul10-05, 09:31 PM
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PF Gold
P: 562
Beta Decay

Quarks are charged, and so already have electromagnetic fields before anything happens.
Igor_S
#5
Jul11-05, 12:21 AM
P: 96
Quote Quote by MarsGhost
What's the explanation of W+/e+ decay? Given set conditions, could an up or down indefinately release electrons and positrons? Or is the mechanism completely different?
Beta + decay is similar: u quark decays into d and W+ boson (which then decays into positron and neutrino). Example of this decay is what danAlwyn described. Energy is maintained by the fact that the final nuclei has lowest energy configuration (that's why it's only possible with protons bound in a nuclei).


As to the second post, EM force between neutron and proton is solely due to their spins. I think this effect is used in neutron scattering experiments on a crystal lattice, for studying lattice vibrations. On a small distances in a nuclei, nuclear force is the dominant one and I guess (since my professor never talked about spin-spin interaction between nucleons) we can ignore it. EM force has nothing to do with beta decays (as I see, it can be ignored), so no photons are emitted.


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