Nucleon and Hyperon Resonances with the Crystal Ball

Abstract

The Crystal Ball Spectrometer is being used at Brookhaven National Laboratory in a series of experiments which study all neutral final states of pi-p and K-p induced reactions. We report about the experimental setup and progress in obtaining new results for the radiative capture reactions pi-p-->gn and K-p-->gL,charge exchange pi-p-->pi0n,two pi0 production pi-p-->pi0pi0n, and eta production pi-p-->eta n reactions. Data have also been obtained on the decays of N*, Delta, Lambda, and Sigma resonances. Threshold eta production has been studied in detail for both pi-p and K-p. Sequential resonance decays have been investigated bystudying the 2pi0 production mechanism both in the fundamental interaction and in nuclei. In addition, we have used the etas produced near threshold to make precision measurements searching in particular for rare and forbidden eta decays.