Test of Direct Reaction Theory from Amplitude Correlations

It is shown that the new proton resonance data on targets $A\sim 48$ provide a crucial check on the validity of direct reaction theory, viz. the existence of amplitude correlations between channels. These are often large ($\left|\rho \right|>~0.5$) and are not simply related to width correlations. Analysis with a simple reaction model shows that the large correlations must imply some failure of the distorted-wave Born-approximation theory of direct reactions.