Fitch, Val Logsdon (1923- )

US physicist. He shared the Nobel Prize for Physics in 1980 with James Cronin for their joint work in particle physics, studying the surprising way certain mesons change from matter to antimatter.

The discovery for which Fitch and Cronin received the 1980 Nobel Prize was first published in 1964. They had set up an experiment with the proton accelerator at the Brookhaven Laboratory in New York to study the properties of K0 mesons. K0 is a mixture of two ‘basic states’ which have a long and a short lifetime and are therefore called K0L and K0S respectively. These two basic states can also mix together to form not K0 but an antimatter particle (anti-K0), and K0 can oscillate from particle to antiparticle through either of its basic states. Fitch and Cronin found that decays of K0L mesons sometimes violate the known rules, and so are different from all other known particle interactions.

Fitch was born in Merriman, Nebraska, and educated at McGill University and Columbia University. He became professor at Princeton University 1960.