Five-particle amplitudes near physical regions

For the hadronic reaction a/sub 4/ + a/sub 5/ yields a/sub 1/ + a/sub 2/ + a/sub 3/ the problem of finding the region of all the physical points where the scattering amplitude is the boundary value of a single analytic function on the mass shell is studied. The problem is illustrated for the reaction p + p yields p + p + pi /sup o/. (LBS)