Cabibbo takes His Place in the World

by Mike Perricone

"Now the world is more closely knit together, but physics was very advanced that way in the 1950s and 1960s, and the experience was incredible," said Cabibbo. "I was at home about half the time, and the rest of the time I was traveling all over. It was a very cosmopolitan experience, which was not common in other ways of life at the time. Some of my closest friends were American, or English."

Cabibbo recently visited Fermilab to attend the Hyperon '99 Conference and to offer a Fermilab Colloquium presentation. His 1963 theory of strange particle decays provided much of the foundation for the Standard Model.

"Very early on, he understood the structure of weak decays involving hadrons," said Keith Ellis, head of Fermilab's Theoretical Physics Department. "The`Cabibbo angle' relates the rate for decays of a strange quark to the decay of a down quark and to the decay of a muon. His theory has grown into the standard model of hadronic weak interactions."

Cabibbo is also the`C' in the CKM Matrix, developed in 1974 (along with Kobayashi and Maskawa), showing that CP violation in weak interactions required three generations of quarks, and thus the existence of six quarks, though only four were known at the time. CP violation, the asymmetry between matter and antimatter, is generally regarded as the reason we exist in a universe of matter with virtually no known antimatter, except for that manufactured in places like Fermilab.

Yet this worldly elder statesman of particle physics quite contentedly lives about the length of a soccer field away from the place where he lived as a child in Rome, during and after World War II.

"I believe that roots are very important, and my roots are not just in Rome but in that particular part of Rome where we always lived," said Cabibbo, "I remember when we were at Cal Tech in 1969, and my son was three years old. From time to time he would say to me,`Papa, you have not forgotten that we must go back to Rome!'"

Though he clearly remembers bombs exploding from Allied air raids, Cabibbo also recalls that the elementary school system in Rome ran uninterrupted during the war. His father was a lawyer, and his mother was a housewife, and Cabibbo recalls his childhood fascinations with astronomy and with building radios as the origins of his sense of inquiry. He traces his formal connection with science from the inspiration of a high school text book titled, "What Is Mathematics?" His university studies in physics led him to nuclear physics and electromagnetism; he wrote his thesis on weak interactions and muon decays.

But a strong sub-theme had marked his development since the end of the war. Cabibbo became a devotee of American literature.

"In Rome, the American embassy had set up an excellent library just after the war," he said. "I would go there often to read and to borrow books. My favorites were Hemingway, Dreiser, Melville. I never finished`Moby-Dick,' but I have read the Polynesian novels,`Typee' and`Omoo.' And Richard Henry Dana,`Two Years Before the Mast.' I read many books about the sea."

Naturally, Cabibbo spent a period of his life as an enthusiastic sailor, owning a 30-foot sailboat named "Panda." He regretfully gave it up because the lack of a good harbor near Rome seriously curtailed his sailing time. But he had plenty of reading time, and he was later introduced to the work of F. Scott Fitzgerald by his wifeóironically and fittingly enough, a professor of modern American literature in Rome.

"Reading`The Great Gatsby' was an interesting experience because I lived many years at Princeton and had often gone to Long Island with friends," Cabibbo said. "So I knew the places Fitzgerald described. I was familiar with`the wasteland' and with the other surroundings."

His openness to ideas lends a context for the process he describes leading up to his break-throughs in the unique concept of quark mixing.

"I was involved in the interactions of high-energy photons with crystals, where the crystal acts as a polarizer," he said. "It was very interesting, but in the end it was not of great practical interest with the advent in the 1960s of colliding beams. We had also been banging on this problem of weak interactions not fitting the universal scheme. I guess there was in my mind a sort of mental interference between my work on photons and crystals, which had to do with polarization, and my work on hyperon decays [mixing]. It was a kind of cross fertilization."

Cabibbo continues to bring ideas together. He has served as president of INFN, Italy's National Institute for Nuclear Physics, which is well represented in Fermilab experiments. He has been engaged for more than 15 years in a project to create computer simulations of weak interactions, and the effects of strong interactions on weak interactions. Those efforts grew into an enterprise for designing and building computers and software. He speaks knowledgeably of the Impressionist collection at the Art Institute of Chicago. He is well versed in the optics and electronics of the high-end camera equipment set up for his photographic portrait in the Fermilab library. And he continues to teach physics, as he has for nearly 30 years.

"Nicola was a great figure even then, but always friendly, always approachable," recalled Ellis, a doctoral student at the University of Rome from 1971 to 1974.

Following Hyperon '99, Cabibbo prepared to return to Rome, to administer a final exam in theoretical physics to his fourth-year students.

"I try not to be too hard on them," he said, his smile growing. "But I would like them to understand nuclear physics."