In a study of 735 000 antiproton annihilations at rest in the hydrogen bubble chamber, 3424 events of the reaction p4-p -* KKinr were observed. We present here the invariant-mass distributions and scatterplots for this reaction, separated according to the three channels KiKnr + ir", Ki(R°)ir + ir~, and i£ii£ ± 7r q V°. Also presented are branching ratios into the various channels. K* production is found to dominate in all cases. The fraction of pp annihilations into K*K* is (4.5±0.9)X10-3 , and into K*Kir is (7.7±1.7)X10" 3 .

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We present here experimental results on the annihilation of stopped antiprotons into KK+3TT, KKr), and KKco. We find the branching ratios for p+p-^KiKm and p+p -> KiKx* to be (0.25±0.04)X10~3 and (1.08±(H6)X10~S, respectively. From events of the latter reaction we find the width of the co meson to be 12.3±2.0 MeV. The E° meson is observed and evidence is seen for the assignment of even charge conjugation and even G parity to this resonance. In addition, we have used events from the reaction p-\-p-~>KiK ± Tr ± to measure the mass difference between the charged and neutral K*. We find MK *« K*©-AfK* ± = 6.3±4.

VOLUME 15, NUMBER 12 PHYSICAL REVIEW LETTERS 20 SEPTEMBER 1965 1.7 1.9 2.1 2.3 MassU-Tr-p) (BeV) 2.5 2.7FIG. 2. (a) Mass of ir~ir + p. (b) Mass of 7r -TT-i >.cay dominantly into any lower mass resonance. The kinetic energies of the proton, TF + and 7r°, were calculated in the center of mass 7T + 77°/) system. The Dalitz plots of the kinetic energy of the if versus the kinetic energy of the proton and the n° versus 7r + were plotted for the events with a TT + TI 0 P mass between (a) 1.65 and 1.69 BeV, (b) 1.69 and 1.725 BeV (the enhancement region), and (c) 1.725 and 1.765 BeV, for the unlikely possibility that a sudden change would occur when passing through the enhancement region. No difference was observed, as was expected due to the complex-ity of the final state.There is no sudden change in the distribution of momentum transfer to the 7r + Tr°p system when the TT + TT°P mass goes through the enhancement region, either. Thus, the only evidence for a resonance is an enhancement in the mass plot of the TT + 7i°p system. Experiments involving the same reaction at neighboring energies have not found any evidence for this enhancement; however, on the basis of their data on the ir + p total cross section, Devlin, Solomon, and Bertsch 1 have recently suggested the existence of a T = § pionnucleon resonance at 1.65 BeV with a width of 0.2 BeV. Their mass is only slightly lower than ours, but their width is much greater.We present in this Letter a tabulation of the rates for the annihilation of antiprotons at rest in hydrogen into various two-body channels. The tabulation is based on an analysis of 9301 two-pronged and 16 700 four-pronged pionic annihilations, and 6768 kaonic annihilations obtained from an exposure of the Columbia-Brookhaven National Laboratory 30-in. hydrogen bub-ble chamber to a separated low-energy antiproton beam at the Brookhaven AGS. The details of the analyses on which this tabulation is based are presented in a series of articles which will be published in the near future. The results are presented in Table I.The fraction of annihilations from the P wave of the pp system was estimated using arguments 532