The earliest accelerator results involving a substantial number of strange particles were obtained at Brookhaven National Laboratory in Upton, Long Island, New York, at the Cosmotron, beginning in 1954. I was fortunate to be a part of that work, which I shall now describe.

By the time the 1954 Rochester conference took place, there appeared to be a number of distinct strange particles. Table 21.1 lists the strange particles as known in that year, my first at Brookhaven. Notice that there is an entry for neutral τ and for an anomalous θ0 that “could be a three-body decay.” Both Λ0 and θ0 were firmly established, and their properties were somewhat clearer than they had been in the past. The next few years saw things become clearer still, largely because of work done at the Brookhaven Cosmotron.

Figure 21.1 shows the setup of experiments at the Cosmotron in that summer of 1954. There were pion beams for total-cross-section measurements with counters. The visual detectors were emulsions and cloud chambers; a few years later they had been displaced by bubble chambers. All those devices were set up to study strange-particle production cross sections and properties. Among other things, K- mesons were put into emulsion. John Hornbostel and Edward Salant showed that K- produce hyperons and estimated a geometric value for the interaction mean free path.

In the early 1950s the most important experimental results were those of William B. Fowler, Ralph Shutt, Alan Thorndike, and William Whittemore with π- in a hydrogen diffusion chamber.