Where does the beta particle come from?

[sweeteviljesus]

In beta decay, as I understand it, a neutron turns into a proton and an electron (plus other stuff too, IIRC) which is ejected from its nucleus at high speed. It is my understanding that electrons (leptons in general for that matter) are fundamental, at least as far as we know. Where does the electron come from? Can I conclude that electron numbers are not conserved? Does a down quark convert somehow into an up quark and an electron?

Thanks for your help,
Rob

[Rysto]

From Wikipedia…

In β− decay, the weak interaction converts a neutron (n0) into a proton (p+) while emitting an electron (e-) and an anti-neutrino

At the fundamental level (as depicted in the Feynman diagram below), this is due to the conversion of a down quark to an up quark by emission of a W- boson; the W- boson subsequently decays into an electron and an anti-neutrino.

[Malodorous]

@sweeteviljesus

Can I conclude that electron numbers are not conserved? Does a down quark convert somehow into an up quark and an electron?

Leptons are conserved (probably), but there are particles that count as anti-leptons, so you can go from zero leptons to a lepton and an anti-lepton. In Beta decay, the electron is “canceled out” by the anti-nutrino.