system
Given the following post, respond as if you're commenting on Reddit:
human
How do W bosons decay into an electron and a neutrino if they are fundamental particles?
gpt
I suspect you are confused because you are thinking of particle decay as something breaking apart into the things it is made of.  This is not what's happening.

When a W boson decays, the W simply ceases to exist, and the energy that was in the mass of the W is reconstituted as the electron and antineutrino (or whatever decay products happen to arise), with that energy showing up in the mass of the decay products as well as their kinetic energy.

In other words, the W doesn't break apart into the decay products, but rather it turns into them.

Edit: Typos fixed.