Strategies of Detection: Interpretive Methods in Experimental Particle Physics, 1930–1950

Between 1930 and 1950 experimental physicists used cloud chambers, coincidence counters, and nuclear emulsions to study both cosmic rays and radioactive processes. In order to identify what particles they were detecting and to measure their properties, these physicists employed a variety of interpretive strategies. Their choice of strategies depended upon what task they were trying to perform, and what instrument they were using. It is argued that different strategies could be employed using the same instrument, that the same strategy could be used with different instruments, and that different strategies could be used in combination with each other. Analyzing the history of the use of these strategies permits a deeper understanding of how physicists designed experiments and used evidence in drawing conclusions. Attending to the patterns of strategy use also permits new periodizations to be developed in the history of particle physics. In the timeframe considered, it is argued that inferential strategies were used to interpret single images of particle tracks, that evidence aggregation was crucial using all kinds of detectors, and that it was also common to use nuclear physics knowledge to narrow the range of possible interpretations. Beginning in the late 1940s, precision measurement, precision experiment design, and decay mode analysis became prominent strategies in the systematic search for new particles. This history builds on and revises Peter Galison’s history of particle detection practices, which is based on the distinct epistemological ideals he supposes drove experimentation in the “image” and “logic” traditions of detector instrumentation.