# [Beta decay] Nuclear physics

1. ### smk

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What is difference between beta particle and electron? I mean in spin, mass or other properties.

14,852
Nothing.

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Thanks

4. ### Simon Bridge

14,852
No worries - conceptually a beta particle comes from a nuclear disintegration, so it is a handy shorthand.
Saying I detected a beta particle from some atom is a bit different from saying I detected an electron from that atom.

Given a free electron, there is no way of telling if it came from a nucleus or an electron shell or pair production even.
You need some other information - like the presence of a beta-unstable radio-isotope, and shielding.

Historically, beta rays were named before they were identified with cathode rays and so with electrons.
Technically beta particles may be positive or negative - but we would usually specify "beta-plus" if the positron is intended.

It's all good fun.

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Thanks alot

6. ### smk

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Thanks I m confused when I studied that in beta decay W- decay into electron and antineutrino. when we see the spin of w- then it is -1.this is TRUE only when electron and antineutrino both have spin half (down).sir this is my own thinking may be I m wrong.thanks

### Staff: Mentor

Beta decay is a process by which a beta particle - which is an electron - is produced along with an antineutrino as a proton converts into a neutron. Yes, this terminology is somewhat confusing.... It came about for historical reasons, because the radiation was observed and given its name before the particles involved were identified and the process understood.

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Thanks

9. ### Simon Bridge

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##p^+ \to n^0 + e^- + \bar \nu_e## does not conserve charge?

You mean: ##n^0 \to p^+ + e^- + \bar \nu_e##

To conserve angular momentum, the electron and neutrino spins need to be aligned - you are thinking.

The usual sin-up/spin-down terminaology only applies in an external magnetic field like that of the nucleus of an atom on in a Stern Gerlach apparatus. There is no "up" or "down" in space.

Odd things can happen in the virtal particle transition though - consider, is total energy conserved as the W -> e+nu. ?

10. ### smk

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Sir you mean that here we cannot consider spin?sir what do you think energy is conserved here.since we know that W is havier .and if we try to re combine electron and antineutrino then what happen?

### Staff: Mentor

D'oh... Yes, of course.

### Staff: Mentor

The W in this case is "virtual". Energy and momentum are conserved, but the mass of a virtual particle is generally not the same as the mass of a "real" particle. Particle physicists often use the jargon "off the mass shell" for virtual particles, where "on the mass shell" means "having the mass that you see in the standard tables."

13. ### smk

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Thanks jtbell

14. ### Simon Bridge

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I think smk wants a definitive answer to the conservation of angular momentum issue ;)
If electron and neutrino spins must be aligned, then that suggests the proton must have the opposite of the spin of the initial neutron.

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Thanks

16. ### smk

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And another question arise here that as we know that in nuclei protons and neutrons occupy definite levels in nucleonic shells.now question is that when neutron transformed into proton then where the proton goes? I mean it will stay in the same level as that of neutron or jump into another level? Thanks

17. ### ChrisVer

In strict language, yes there would be a small jump(due to coulomb potential). The nucleus itself can change.. but in general and simple models this doesn't happen, because the strong force doesn't distinguish between neutrons and protons (isospin symmetry).

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Thanks

### Staff: Mentor

To be small, you need very special nuclei like Tritium.
In general, neutron and proton numbers in a nuclei are so different that the most high-energetic occupied neutron state and the available unoccupied proton states have different quantum numbers.

20. ### ChrisVer

hmm... Do for example the higher atomic number mirror nuclei differ much from each other?