James Watson Cronin
Cronin, James Watson (1931-) is an American nuclear physicist who shared the 1980 Nobel Prize in physics with his colleague, American physicist Val Logsdon Fitch. They discovered the violations of fundamental symmetry principles in the decay of neutral K-mesons. This is just one of several contributions Cronin has made to elementary particle physics.
James Cronin was the son of James Farley Cronin and Dorothy Watson Cronin. In 1939, the family moved to Dallas. There his father taught Latin and Greek at Southern Methodist University, and James Cronin attended local public elementary and high schools. In 1947, James Cronin entered Southern Methodist University and majored in physics and math. In 1951, he received his bachelor's degree. He then entered the University of Chicago as a graduate student. earned his master's degree in 1953, and immediately went to work on his doctorate, which he received in 1955.
While at the University of Chicago, Cronin was very much influenced by the work of Murray Gell-Mann, who went on to receive the Nobel Prize in physics in 1969 for the development of a system of classifying elementary particles according to a quality called strangeness.
After receiving his doctorate, Cronin joined the Brookhaven National Laboratory in New York as an assistant physicist. He spent three years at the laboratory, during which time he met Fitch. In 1958, Fitch invited Cronin to join him at Princeton University. Cronin accepted and became an assistant professor of physics at Princeton. Cronin and Fitch soon began the work that would eventually lead to their winning the Nobel Prize. In 1965, Cronin became an associate professor of physics.
The foundation of Cronin and Fitch's research was a classic experiment suggested in 1956 by Tsung Dao Lee and Chen Ning Yang on the conservation of parity during certain nuclear reactions. One of the most fundamental laws of physics at that time was the principle of conservation of parity, which states that there is symmetry between an event and its mirror image, with both satisfying identical laws of nature. In 1956, Lee and Yang proposed that the property known as parity might not be conserved in some nuclear changes. Their experiments showed that parity was not conserved in a type of nuclear event called a weak interaction. An example of such an event is the emission of an electron by a radioactive nucleus. Soon after they revealed their theory, Chien-shiung Wu disproved the law of the conservation of parity, confirming their theory. The discovery raised a number of issues for theoretical physicists, including whether other types of symmetry could also be violated. Lee and Yang suggested that it could be possible that the combination of parity (P) and another property, charge conjugation (C), was conserved even if each alone was not.
In 1963, Cronin and Fitch began their research that led to evidence for the concept of CP violation. The intent of their experiments was to investigate the K-mesons decays. During the course of their work, they discovered examples of CP violation. They announced their findings in 1964.
In 1971, Cronin left Princeton and returned to the University of Chicago, where he was appointed professor of physics and conducted research. He eventually became an emeritus professor with the university.
Cronin has since held a teaching position with the University of Utah's department of physics. He and Alan Watson, a University of Leeds (United Kingdom) professor, are leading the Pierre Auger Project, a worldwide effort to study the highest energy cosmic rays. There are 250 scientists in 19 nations working on the project, which involves the construction of an observatory with cosmic-ray detectors located in Millard County, Utah, and in Argentina.