Illustration: Carin Cain

Figure 1: Electrons in an atom interact with the nucleus through the electromagnetic force via the exchange of massless photons ($γ$). The weak force is mediated by $Z0$ bosons. The weak effects by themselves are too small to see directly. However, it is possible to measure the effect of $Z0$ boson exchange between an electron and a neutron by looking at the quantum mechanical interference between this process (right) and the electromagnetic interaction (left). The figure provides a pictorial representation of how the quantum interference between the two processes—the sum of the amplitudes squared—contributes to a measureable signal.