Beta particle is made up of electron or positron.
[tex]\beta ^{-}:\\\\
^{A}_{Z}E \ \Rightarrow \ ^{ \\ \ A}_{Z+1}Y \ + \underbrace{^{\ \ 0}_{-1}e}_{electron} \ + \ \nu\\\\
\beta ^{+}:\\\\
^{A}_{Z}E \ \Rightarrow \ \ ^{ \ \ \ A}_{Z-1}Y \ + \ \underbrace{^{\ \ 0}_{+1}e}_{positron} \ + \ \nu[/tex]
