Giuseppe Occhialini and CERN

Abstract

It is almost a paradox that Giuseppe Occhialini, Beppo for the older generation, never had any formal connection with CERN. Yet he had an influence on its creation and on its physics. His achievements provided some of the best arguments for having such a new laboratory, while his personality and his example had a lasting impact on many young and talented cosmic ray physicists who later made CERN a scientific success and an example of international collaboration. This was Beppo’s first legacy to CERN, and to give an idea of how this happened I shall briefly try to evoke a few testimonies from the early fifties. In 1948 Occhialini was back in Italy, first in Genoa and then, in 1952, in Milan, where he soon formed a strong group for the study of high-energy physics using nuclear emulsions, a branch of research that he had first pioneered in Bristol and then in Brussels. At that time, the discovery of the pion was already well known beyond the scientific world: at school, it was our history, and not our physics teacher who first told us about the then newly observed particle, which he described as “the glue which keeps matter together”. Most of the experimental activity on the properties of the pion, however, had already moved from cosmic rays to the synchro-cyclotrons of Berkeley, Columbia and Chicago. Nevertheless, cosmic ray physicists still had a few years of discovery before them exploring a new type of unstable particles discovered soon after the pion, and later, in light of the riddle between their copious production and their long lifetimes called “strange”.