James Cronin

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James Cronin
Born James Watson Cronin
(1931-09-29)September 29, 1931
Chicago, Illinois, U.S.
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Saint Paul, Minnesota, U.S.
Nationality American
Fields Physics
Institutions University of Chicago
Alma mater Southern Methodist University
University of Chicago
Known for Nuclear physics
Notable awards E. O. Lawrence Award (1976)
Nobel Prize in Physics (1980)
John Price Wetherill Medal
National Medal of Science

James Watson Cronin (September 29, 1931 – August 25, 2016[1]) was an American particle physicist.[2][3]

Cronin was born in Chicago, Illinois, and attended Southern Methodist University in Dallas, Texas. He and co-researcher Val Logsdon Fitch were awarded the 1980 Nobel Prize in Physics for a 1964 experiment that proved that certain subatomic reactions do not adhere to fundamental symmetry principles. Specifically, they proved, by examining the decay of kaons, that a reaction run in reverse does not merely retrace the path of the original reaction, which showed that the interactions of subatomic particles are not invariant under time reversal. Thus the phenomenon of CP violation was discovered.[4][5][6][7]

Cronin received the Ernest Orlando Lawrence Award in 1976 for major experimental contributions to particle physics including fundamental work on weak interactions culminating in the discovery of asymmetry under time reversal. In 1999, he was awarded the National Medal of Science.[8]

Cronin was Professor Emeritus at the University of Chicago winning the prestigious Quantrell Award[9] and a spokesperson emeritus for the Auger project. He was a member of the Board of Sponsors of the Bulletin of the Atomic Scientists.


James Cronin was born on September 29, 1931 in Chicago, Illinois, where his father, James Farley Cronin, was a graduate student of classical languages at the University of Chicago. After his father had obtained his doctorate the family first moved to Alabama, and later in 1939 to Dallas, Texas, where his father became a professor of Latin and Greek at Southern Methodist University. After high school Cronin stayed in Dallas and obtained an undergraduate degree at Southern Methodist University in physics and mathematics in 1951.[10]

For graduate school Cronin moved back to Illinois to attend the University of Chicago. His teachers there included Nobel Prize laureates Enrico Fermi, Maria Mayer, Murray Gell-Mann and Subrahmanyan Chandrasekhar. He wrote his thesis on experimental nuclear physics under supervision of Samuel K. Allison. While in graduate school he also met his wife, Annette Martin, whom he married in 1954.[10] With Annette he had three children Cathryn (1955), Emily (1959), and Dan (1971)

After obtaining his doctorate in 1955, Cronin joined the group of Rodney Cool and Oreste Piccioni at Brookhaven National Laboratory, where the new Cosmotron particle accelerator had just been completed. There he started to study parity violation in the decay of hyperon particles. During that time he also met Val Fitch, who brought him to Princeton University in 1958. Together they studied the decays of neutral K mesons, in which they discovered CP violation in 1964. This discovery earned the duo the 1980 Nobel Prize in Physics.[10]

After the discovery, Cronin spent a year in France at the Centre d'Etudes Nucleaires at Saclay. After returning to Princeton he continued studying the neutral CP violating decay modes of the long-lived neutral K meson. In 1971, he moved back to the University of Chicago to become a full professor. This was attractive for him because of a new 400 GeV particle accelerator being built at nearby Fermilab.[10]

When he moved to Chicago, he began a long series of experiments on particle production at high transverse momentum. With physicist Pierre Piroue and colleagues we learned about many things. These are summarized in Physical Review D, vol 19, page 764 (1977). Following these experiments Cronin took a sabbatical at CERN in 1982-83 where he did his last experiment, a measure of the lifetime of the neutral pion (Physics Letters vol 158 B page 81 (1985). He then switched to the study of cosmic rays. The first was a series of measurements looking for point sources of cosmic rays. No sources were found. A summary of the measurements was published in Physical Review D vol 55 page 1714 (1997). Following this experiment he with Alan Watson and Murat Boratav organized an international collaboration to study cosmic rays with energies greater than 10 to the 19 eV. (It was called the Pierre Auger Observatory and is still running (2013) in Mendoza Province Argentina.) A description of the observatory is given in Nuclear Instruments and Methods A. vol 523 page 2004 (2004).

Personal life

Cronin was married to Annette Martin. She was the Director of Special Events at Roosevelt University.[11] They have three children: two daughters, Cathryn and Emily, and a son, Daniel.[10] In June 2005 Annette Martin died of complications of Parkinson's disease. She was 71.[11]

In November 2006 he married the former Carol Champlin.

In May 2011 his daughter Cathryn Cranston died of leukemia at age 54.


Abraham J., Cronin J. W. et al., Observation of suppression of the Flux of Cosmic Rays above 4x10**19 eV., Phys Rev Letters vol 101, p 061101, (2008).


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  8. National Science Foundation - The President's National Medal of Science
  9. [1]
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External links