Physicists have struggled for seven decades with the question of why there is more matter in the universe than antimatter.

Protons and neutrons are usually made up of three quarks. For protons that's two up quarks and one down quark, for neutrons, ...

Here is the equation for the alpha decay of radon-219 into polonium. Beta decay involves the conversion of a down quark to an up quark. This changes a neutron into a proton plus an electron.