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The Princeton-Pennsylvania accelerator 15-in. hydrogen bubble chamber was used to investigate r+p associated production a t 1.7 GeV/c. Approximately 4000 events were found; about half of these were in the Z+Kf channel. The AKf?r+ channel dominates the remaining half of the data. We find evidence for the existence of a T = 1 hyperon resonance a t 1475f 15 MeV with a width of 3 0 f 15 MeV in the AK+r+, Z+K+7r0, Z°K+?r+, and ~~+ z " c h a n n e l s .The cross sections of the strange-particle channels and the branching ratios of various resonances are also presented.

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Since the discovery of the Fj*(1385), there has been continuous speculation concerning the existence of a pion-hyperon resonance with isospin r = 2, but experiments to date have failed to find any evidence for its existence.^'^ To further this investigation, we studied the reaction K' 4-w(C)-S" +7r" +7r"'' +recoils (1) in a 1.15-BeV/c K' interaction on neutrons in carbon in the Berkeley 30-in. propane chamber.The reaction /C"+w(C)-S"^+77"+7r'+recoils^oes not give any information concerning any r = 2 resonance, but has been studied for completeness. We also studied the reactionto see how a well-known resonance is produced in carbon. For the charged pionic decays, the scan-table identification of sigmas depended completely on the ionization change at the decay point. This criterion did not bias against higher momentum sigmas,^ but did give a bias against events where the pion track from the sigma decay was steep in the chamber. A total of 330 events of the type (1) was found in our scanning. The lifetime measured for S" from the events [(1.12± 0.20)xl0'^° sec] agrees with the accepted value.The pion tracks involved in this experiment were generally long, and the momenta were determined by curvature measurements to approximately 12% on the average. However, the average Sigma track length was 1.1 cm, and only a minimum value of the momentum could be obtained from range measurements. The angle of decay and the pion momentum were used to calculate the momentum of the sigma at the decay point. About half of the time, this resulted in solutions that were double-valued corresponding to forward or backward decay of the sigma in the center-of-mass (cm.) system. For most of these events, ionization of the sigma was used to resolve this ambiguity. For the few cases where the ambiguity was not resolved by sigma ionization, the two solutions were equal within the errors, and the average value was used. The range-momentum relationship was then used to find the sigma momentum at the production vertex, but no constraints were applied at this point.To observe resonances in the invariant-mass plot, we needed to know the phase space involved. Since, in our case, we had a variable cm. energy available due to the Fermi momentum of the nucleons in the carbon nucleus, we adopted the following procedure to calculate the phase space:277

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