Nuclear Physics B97 (1975) 317-330 © North-Holland Publishing Company IMPACT PARAMETER ANALYSIS OF THE PROCESSES pp ~- ppzr+lr - AND ,r-p -~ ~r-prr+Tr - * B.R. WEBBER Cavendish Laboratory, Cambridge, England D.M. CHEW ** Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720, USA M.J. COUNIHAN CERN, Geneva, Switzerland H. YUTA *** Argonne National Laboratory, Argonne, Illinois 60439, USA Received 28 April 1975 A new method of obtaining an experimental lower bound on the r.m.s, impact para- meter of an exclusive process is applied to data on pp ~ ppn+n - at 7-25 and 205 GeV/c and on *r-p ~ 7r-pn+~r- at 16 and 205 GeV/c. The overall lower bounds are compared with geometrical and multiperipheral model predictions, and are shown to rule out the version of the geometrical model in which these processes become central at high ener- gies. Our results for diffractive regions of longitudinal phase space favour a peripheral impact parameter profile for inelastic diffraction. In a related study of transverse mo- mentum correlations in these processes, we find a predominance of "nearest-neighbour" correlations between transverse momentum transfers. 1. Introduction Although a great deal is now known about the impact parameter structure of elastic scattering at high energies [1 ], almost nothing is known about the impact parameter dependence of any other exclusive process. Even the most rudimentary * Work supported in part by the US Atomic Energy Commission, the National Science Foun- dation, and the UK Science Research Council. ** On leave from the Universit6 de Paris VI, Paris, France. *** Present address: Physics Department, Tohoku University, Sendai, Japan 980.