18 - Pure and Hybrid Detectors: Mark I and the Psi

Summary

The broad sweep of theoretical claims and programs commands our attention: even the title of this book, The Rise of the Standard Model, points to theory as the capstone of physics. But outside the commitment of theorists to principles of their practice such as causality, determinism, unification, and symmetry breaking, there are commitments built into the hardware of the laboratory. Less dramatic perhaps, less often spoken of without doubt, these traditions of instrumentation shape the practice of experimental physics and embody views about the nature of acceptable empirical evidence. In this chapter, I want to explore the coming together of two great lines of instruments in the twentieth century: on one side, the image tradition instantiated in the sequence cloud chambers, nuclear emulsions, and bubble chambers. These devices make pictures, the delicate array of crisscrossed lines that have come to serve as symbols not only of particle physics but of physics more generally. On the other side, there stands a competing logic tradition, this one aiming not to make pictures but instead to produce counts – the staccato clicks of a Geiger–Müller counter rather than the glossy print from a cloud chamber. In the line of such counters came a host of other electronic devices that built their persuasive power not through the sharpness of images but through the accumulation of a statistically significant number of clicks.