Structure ofANN(90°)

It is suggested that, just as the differential cross section at 90° for proton-proton elastic scattering oscillates, so does the spin-correlation parameter $A_{\mathrm{NN}}$ at 90°. The oscillations appear to be around the quark-model value of $\frac{1}{3}$, with a periodicity corresponding to an interaction radius of about 0.8 fm.