In the process of particle decay (eg carbon-14 ---> nitrogen-14), is there any relations with radioactivity? Is it reversible? ( up quark + 2 x down quark + W positive boson = down quark + 2 x up quark + electron, so that carbon-14 turns to nitrogen-14. Is it possible that down quark + 2 x up quark + W negative boson = up quark + 2 x down quark + ? , so that nitrogen-14 can turn back to carbon-14? If possible, what's that '?' ?