8  Weak interactions

Weak interactions manifest themselves as reactions, or decays, in which some particles may disappear, while others appear. There is no structure that is bound together by a ‘weak force’, but weak interactions are vital for understanding the world around us.

Weak interactions were involved in most of the reactions in the very early Universe by which particles changed from one sort to another. They are therefore largely responsible for the overall mixture of particles from which the current Universe is made.

The most common example of a weak interaction is beta-decay and, as you saw earlier, there are three related processes, each of which is a different type of beta-decay. In each of these three processes the nucleus involved will change from one type of element to another, as a result of either increasing or decreasing its proton content by one. Each process relies on the weak interaction.