Nobel Prizes and Laureates

Nobel Prizes and Laureates

The Nobel Prize in Physics 1980
James Cronin, Val Fitch

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James Cronin - Facts

James Watson Cronin

James Watson Cronin

Born: 29 September 1931, Chicago, IL, USA

Affiliation at the time of the award: University of Chicago, Chicago, IL, USA

Prize motivation: "for the discovery of violations of fundamental symmetry principles in the decay of neutral K-mesons"

Field: particle physics

Prize share: 1/2

A Small but Clear Lack of Symmetry

For a long time, physicists assumed that different types of symmetries characterise nature. In a kind of mirror-world, the physical laws should be the same if right and left are exchanged and if matter is replaced by antimatter. The left-right symmetry had already been shown to be violated when James Cronin and Val Fitch in 1964 discovered that in the decay of the neutral K-meson the matter-antimatter symmetry is also violated. They could also show that symmetry under time-reversal is not valid: reactions going backward in time are not identical to those going forward.

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