The experimental discovery of CP violation

Abstract

[This address was presented by James W. Cronin as the Nishina Memorial Lecture at the University of Tokyo, and at Yukawa Institute for Theoretical Physics in September, 1993.] The discovery of CP violation was a complete surprise to the experimentalists that found it as well as to the physics community at large. This small effect means that the symmetry means that the symmetry between the behavior of matter and antimatter is not exact. The experiment that made the discovery was not motivated by the idea that such a violation might exist. I will describe in some detail how it came to be performed in the context of of the fast moving pace of particle physics in 1963. I will review how we actually did the experiment using extracts from personal notebooks. I will discuss some difficulties we had with the apparatus and the anxiety some of us had to be sure we were correct. Such considerations are rarely revealed in a formal publication but are the realities of doing science. I will then discuss the aftermath of the experiment and the great efforts that continue to this day to understand the origin of the CP violation, which remains a mystery. The search for the origin of CP violation motivates many of the proposals for new particle facilities. © Nishina Memorial Foundation 2008.