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Jack Steinberger, Fermi’s student who laid the foundation for the concept of weak interaction

A story written by Storie Scientifiche for the Enrico Fermi Research Center.

Born as Hans Jakob, he emigrated at the age of thirteen from Bavaria to the United States. He began studying chemical engineering at Armor Institute of Technology (now Illinois Institute) but dropped out after only two years to contribute to the family economy.

In 1942, he earned a degree in chemistry from the University of Chicago. One of his first contacts with physics, and physicists, came after his enlistment in the U.S. Army. With the War over, he returned to study at the University of Chicago.

Steinberger had had several problems with the physics curriculum: he had failed to pass the required exams before starting his doctoral thesis. When he received a second chance, Fermi asked him to become his assistant for a course in elementary physics, and after passing the exams, Fermi agreed to become his supervisor.

On Fermi’s advice, Steinberger devoted himself to examine a problem raised by an experiment performed by Bruno Rossi. While observing the decay of muons, created in turn by the decay of pions in cosmic rays, they “counted” a number of electrons lower than expected (there was an error of a factor two).

Once again Fermi intervened, suggesting him to perform an experiment that lasted less than a year, coming to the conclusion that in muon decay, electron was accompanied by two neutral particles ( “probably neutrinos”). This experiment laid the experimental foundations for the concept of weak interaction.

Steinberger recalled his time as a student with Fermi with these words:

“I am greatly indebted to Fermi. His courses were jewels of simplicity and clarity. He helped us to become good physicists, not limiting himself to normal classroom work but organizing evening discussions on a wide range of topics.”

Continuing his work as an experimentalist in the field of particle physics he went on to win the Nobel Prize in 1988, a prize he shared with Leon Lederman and Melvin Schwartz, for the discovery of the muon neutrino.