The muon anomalous magnetic moment has been measured in a new experiment at Brookhaven. Polarized muons were stored in a superferric ring, and the angular frequency difference, v a , between the spin precession and orbital frequencies was determined by measuring the time distribution of highenergy decay positrons. The ratio R of v a to the Larmor precession frequency of free protons, v p , in the storage-ring magnetic field was measured. We find R 3.707 220͑48͒ 3 10 23. With m m ͞m p 3.183 345 47͑47͒ this gives a m 1 1 165 925͑15͒ 3 10 29 (613 ppm), in good agreement with the previous CERN measurements for m 1 and m 2 and of approximately the same precision.

We report on precision measurements of the cross sections for the reactions p p→⌳ ⌳, p p→⌳ ⌺ 0 , and p p→⌺ 0 ⌳ in the region below 5 MeV excess kinetic energy above reaction threshold. For the p p→⌳ ⌳ measurement, the data represent a third and definitive scan through the threshold region by this experiment. Improvements in the detector system and analysis techniques, coupled with greatly increased statistics, have negated the question of the existence of a near-threshold resonance as had been indicated in our earlier, lower-statistics studies. The high statistics permit the first extraction of the polarization information at these low energies. We also report the first measurement of the cross section for the complementary reactions p p →⌳ ⌺ 0 ϩc.c. at excess energies up to 2.5 MeV. This allows a comparison of the onset of ⌳ ⌳ production to that of ⌳ ⌺ 0 and ⌺ 0 ⌳. The data show no evidence for near-threshold resonance structures in either reaction channel. Further, the p p→⌳ ⌺ 0 ϩc.c. reactions exhibit a larger P-wave fraction close to threshold compared to p p→⌳ ⌳.

The reactionpp →ΛΛ →pπ + pπ − has been measured with high statistics at a beam momentum of pp = 1.637 GeV/c. The use of a transversely-polarized frozen-spin target combined with the self-analyzing property of Λ/Λ decay allows access to unprecedented information on the spin structure of the interaction. The most general spin-scattering matrix can be written in terms of eleven real parameters for each bin of scattering angle, each of these parameters is determined with reasonable precision. From these results all conceivable spin-correlations are determined with inherent self-consistency. Good agreement is found with the few previously existing measurements of spin observables inpp →ΛΛ near this energy. Existing theoretical models do not give good predictions for those spin-observables that had not been previously measured.

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