Er ... there are lots of nuclear decays which produce beta particles electrons. Neutrons have a short half-life when free of a nucleus, and decay into a proton, electron and an electron anti-neutrino (to conserve momentum). [1]
Electrons are posited to be fundamental, and e-e e-e<sup>+</sup> collisions haven't, as far as I know though well outside my original field of study, produced any data suggesting internal structure.
This doesn't mean that they don't have structure, we simply have no theory (that I know of, but then again, I'm a former solid state guy) that predicts structure, nor do we have sufficiently powerful colliders to get us to a point to see such structure.
Electrons are posited to be fundamental, and e-e e-e<sup>+</sup> collisions haven't, as far as I know though well outside my original field of study, produced any data suggesting internal structure.
This doesn't mean that they don't have structure, we simply have no theory (that I know of, but then again, I'm a former solid state guy) that predicts structure, nor do we have sufficiently powerful colliders to get us to a point to see such structure.
[1] https://en.wikipedia.org/wiki/Beta_decay#%CE%B2%E2%88%92_dec...