The measured quantity is the difference in the number of gamma rays emitted within a solid angle between the two neutron spin states. This difference (divided by the sum) forms an asymmetry with possible parity-violating and parity-conserving components, where the former is known as A γ γ . By studying the parity-violating correlation between the spin of the incoming neutron (its polarization) and the direction of the emitted gamma ray, one primarily probes h π π (traditionally known as f π π ), the long-range coupling constant used to describe the hadronic weak interaction.