I am a casual follower of physics and was recently watching a YouTube video on Neutron stars. I am looking for a "simple" answer to this question. Per the video when the star collapses with the right mass to form a neutron star, at some point gravity forces electrons into protons and flips an Up quark into a down quark and a neutrino, resulting in a change from a proton to a neutron. The question is what is the process that flips the Up to a Down quark, is the electron directly absorbed by one of the Up Quarks, or is there a force carrier particle in the process, like photons? That is really the main question and may lead to others, like is the electron acting like a particle or a wave when this happens and how does it single out 1 up quark to flip... Thanks in advance to anyone that can help out on this.