Just further to what nrqed said a couple of examples of beta decay;
Beta
+ Decay:
[tex]p \rightarrow n + \upsilon_{e} + e^{+}[/tex]
Beta
- Decay;
[tex]n \rightarrow p + \overline{\upsilon_{e}} + e^{-}[/tex]
I was going to draw Feynman diagrams but then I realised PF doesn't support them in latex
