system
Given the following post, respond as if you're commenting on Reddit:
human
For beta decay: During positron emission a proton becomes a neutron and emits a positron (and neutrino). During electron emission a neutron becomes a proton, emitting an electron (and antineutrino). How is it possible that they can convert back and forth by continuously losing particles?

I've had this question for a while. It doesn't make sense that they can convert into each other by losing particles each time. Can someone please explain.
gpt
A proton is made of 2 up quarks and 1 down quark.  A neutron is 2 down quarks and 1 up quark.

In beta- decay, an up quark converts to a down quark, and emits a W- boson.  This boson decays to an electron and an antineutrino.

In beta+ decay, a down quark converts to an up quark and emits a W+ boson, which decays to a positron and a neutrino.

So at the nucleus level, what you see is a proton change to a neutron and vice-versa.  But what is actually happening has to do with quarks flipping back and forth.

One other thing to note is that the neutron has more mass than the proton.  As a result, a free neutron can beta- decay, but a free proton cannot beta+ decay.  The reaction isn't reversible (in that sense).  Beta+ decay can only occur in bound nuclear states, where some of the binding energy can go into the mass needed.