Proposal to study the reactions p + p --> p + (p + pi+ + pi-) / (n + pi+) at 200-GeV and 500-GeV

We would like to study isobar formation at 200-500 GeV in the moderate t-range (-0.1>t>-0.4), concentrating on the modes (p{pi}{sup +}{pi}{sup -}) and (n{pi}{sup +}). These isobar decay modes have such strong signatures that every event will be fully reconstructed with at least a 1C fit even without momentum analysis. Existing evidence is that these modes are either dominant or very strong in the cases of several known isobars. Logistically, our experiment is designed to be suitable for the initial phase of operation of the NAL accelerator. We require only a diffraction-scattered proton beam. The apparatus required is small, simple, and compact enough to be located in the machine tunnel. We do not require a magnet or any rigging, and at least the first results can be obtained with a polyethylene target. the data rate should be very high, and the information gained should be very informative on possible microstructure in the baryon mass spectrum, on the interaction properties of the Pomeron, and on the possible utility of the double-Ragge model and the Veneziano four-point function. A 28.5 GeV run of this experiment has been approved as experiment number 533 at the AGS, and will take place during October '70-Maymore » '71. That run will test all of the same apparatus needed for the NAL experiment.« less