These questions came to mind after my physics teacher told us that a neutron is actually a "proton-electron" pair. He then said in beta minus decay, when the neutron decays, the electron is released and only the proton remains. I'm pretty sure this is incorrect, though, but can any confirm it? I get that the proton is made up of 2 up quarks and 1 down quark, and the neutron is 1 up quark and 2 down quarks. Can anyone confirm or deny if my following understanding of this process is correct?... In beta minus decay, a down quark in a neutron decays into an up quark. This releases a W- Boson, which then decays into an electron and an electron anti-neutrino upon exiting the nucleus. Now, the questions... 1) How does the down quark decay into an up quark? I've read several different explanations for this, including that virtual electron-positron pairs pop into and out of existence in the nucleus, and the positron can give the +1 charge to the down quark needed to change it into an up quark (explains conservation of charge). 2) Lepton number has to be conserved, which is why the electron and the electron anti-neutrino are created. Does the W- Boson have exactly the mass of the electron + neutrino?