Positron Emission

Another particle that a nucleus can emit during a decay is a positron (⁰₁e). A positron is just like any other electron, except it has a positive charge (weird, huh?). For example, Carbon-11 decays by positron emission:

11 11 0 C → B + e 6 5 1

So where are all of these positrons? Since positrons are anti-matter, they don't exist for very long. As soon as they collide with a normal electron (which are everywhere), they destroy each other and produce energy in the form of gamma rays.

0 0 0 e + e → 2 γ 1 -1 0