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Steinberger, Jack

nuclear neutrinos kinds neutrino

[ stiyn berger] (1921– ) US nuclear physicist: a major contributor to the ‘standard model’ of particle physics.

Steinberger went to the USA in 1934 as a teenage Jewish refugee, and later studied chemistry at Chicago. In the Second World War he worked in the radiation laboratory at Massachusetts Institute of Technology and his interest moved to physics; as a result, he worked for his PhD in Chicago on the muons present in cosmic rays. He showed that a muon decays to give an electron and two neutrinos; and he continued his work in this field with M Schwartz (1932– ) and L Lederman (1922– ) at Columbia University, New York, from 1959. They theorized that neutrinos should be of two kinds, the electron neutrino and the muon neutrino. In the early 1960s a new high-energy proton accelerator became available at the Brookhaven National Laboratory, which could provide enough neutrinos to test their theory. To exclude other particles, a filter was used consisting of a stack of steel plates from a scrapped battleship, 13.5 m thick. Behind this a detector located a few nuclear reactions that confirmed that two kinds of neutrino exist.

Working in Europe at CERN near Geneva from 1968, Steinberger continued to use neutrinos to study nuclei and nuclear forces. The current ‘standard model’ for nuclei proposes two types of component as fundamental units of matter: the quarks and the leptons. Of the six kinds of quark, three have electric charge 2/3 and three have –1/3 of a proton’s charge. All are subject to the strong nuclear force. They also have a new form of charge (‘colour’) and ‘spin’. None have been found free; they are permanently confined in nuclei. All matter is made of quarks (eg the proton and the neutron are made of three quarks, of different kinds) together with leptons, which are also of six kinds. Leptons are light particles (electrons, muons, tau and their neutrino partners). The neutrinos interact only through the weak nuclear force: muons and tau particles are short-lived.

The present picture of the fundamental particles of matter will certainly change in the future, probably with the development of higher energy particle accelerators, as in the past. Steinberger, Lederman and Schwartz shared the Nobel Prize for physics in 1988.

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