Reactionp¯+p→Y¯+Y

The study of the interaction $\overline{p}+p\to \overline{\Lambda }+\Lambda$, performed with the 72-inch hydrogen bubble chamber, has yielded 11 of these events in a total of 21 100 antiproton interactions at 1.61 Bev/c. The cross section for $\overline{\Lambda }+\Lambda$ production was estimated as 57±18 μb. Eight of the 11 antilambda particles went forward in the c.m. system. At the higher momentum of 1.99 Bev/c, one single-$V$ and one double-$V$ event fitting $\overline{\Lambda }+\Lambda$ production unambiguously and one single-$V$ and one double-$V$ event fitting ${\overline{\Sigma }}^0+\Lambda$ or ${\Sigma }^0+\overline{\Lambda }$ were observed in 4920 antiproton interactions. These events yield a $\overline{\Lambda }-\Lambda$ production cross section of 55±40 μb; this value is consistent with that predicted by the ratio of phase space on the basis of the 1.61-Bev/c data. No charged antisigma events were observed at the higher momentum. Three stages of particle separation utilizing velocity-selecting spectrometers were employed. At the lower momentum, background pions were one-third as numerous as antiprotons at the bubble chamber and the flux of antiprotons was about one per picture. At the higher momentum, the background pion to antiproton ratio was 1.8, and the flux of antiprotons was one every 6 pulses. Delta rays on incident interacting tracks were used to determine beam composition.