PROTON-PROTON SCATTERING AT 90-DEGREES FOR P(LAB) UP TO 12 GEV C/

We examine the problem of pp scattering at 90 degrees in the center of mass. It is useful to consider amplitudes with certain invariant char acteristics to understand the behavior of the cross section and spin o bservables. We find that a partial consideration of multiple pion exch anges provides a qualitative explanation of the minima as a function o f energy seen in the data.