P−Ain intermediate energy inelastic scattering

The difference between the polarization, $P$, and analyzing power, $A$, in inelastic scattering by a spin ½ projectile is shown to be proportional to the reaction $Q$-value. This follows from parity and time reversal symmetry only. At intermediate energy (500-1000 MeV) analyticity suggests that $Q$ scales with $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}$ so that $\mathrm{}|P-A|\mathrm{}\le \frac{Q}{E_{\mathrm{c}.\mathrm{m}.\mathrm{}}}$, and hence that $\mathrm{}|P-A|\mathrm{}$ is very small.