I'm no physicist and I won't pretend that I understand any of those words, so this will probably not make any sense. But I'm curious how particle decay would b

I'm no physicist and I won't pretend that I understand any of those words, so this will probably not make any sense. But I'm curious how particle decay would be like for a particle with a de Broglie wavelength of several lightyears, and how would that be affected by the speed of causality. (EDIT: Or even a few light-minutes (like from Earth to Sun) or whatever distance where we no longer have the luxury of "things looking instantaneous".)