Topic 22 – Decays, Scattering, and the Golden Rule Pre‐Lecture Reading/Post‐Lecture Summary From the title of this lecture you might think this is something of a kindergarten level lecture. Nope! Not even close. Today we begin our sojourn into calculations, that is getting some hard won numbers that we can carry over to experimentalists and say “Hey! Go check this.” We will start by defining two of the more important quantities we want to calculate and then review a standard framework which handles almost half of the work for us, this being the “Golden Rule” attributed to Enrico Fermi. We will learn what the Golden Rule actually covers and what it does not. Then you will leave and be happy.