Full Idea
The quantum field theory of the weak force needs three carrier particles. The W+ and W- are electrically charged, and enable the weak force to change the charge of a particle. The Z° is uncharged, and mediates weak interactions with no charge change.
Gist of Idea
Three particles enable the weak force: W+ and W- are charged, and Z° is not
Source
New Scientist writers (Why the Universe Exists [2017], 02)
Book Reference
New Scientist writers: 'Why the Universe Exists' [John Murray 2017], p.28