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Experimental Observation of the Intermediate Vector Bosons W⁺, W^- and Z⁰

Stochastic Cooling and the Accumulation of Antiprotons

"for their decisive contributions to the large project, which led to the discovery of the field particles W and Z, communicators of weak interaction"

Carlo Rubbia	Simon van der Meer

1/2 of the prize	1/2 of the prize
Italy	the Netherlands
CERN Geneva, Switzerland	CERN Geneva, Switzerland
b. 1934	b. 1925

Autobiography: Carlo Rubbia

I was born in the small town of Gorizia, Italy, on 31 March, 1934. My father was an electrical engineer at the local telephone company and my mother an elementary school teacher. At the end of the World War II most of the province of Gorizia was overtaken by Yugoslavia and my family fled to Venice first and then to Udine.

As a boy, I was deeply interested in scientific ideas, electrical and mechanical, and I read almost everything I could find on the subject. I was attracted more by the hardware and construction aspects than by the scientific issues. At that time I could not decide if science or technology were more relevant for me.

After completing High School, I applied to the Faculty of Physics at the rather exclusive Scuola Normale in Pisa. My previous education had been seriously affected by the disasters of the war and the subsequent unrest. I badly failed the admission tests and my application was turned down. I forgot about physics and I started engineering at the University of Milan (Politecnico). To my great surprise and joy a few months later I was offered the possibility of entering the Scuola Normale. One of the people who had won the admission contest had resigned! I am recollecting this apparently insignificant fact since it has determined and almost completely by accident my career of physicist. I moved to Pisa, where I completed the University education with a thesis on cosmic ray experiments. They have been very tough years, since I had to greatly improve my education, which was very deficient in a number of fundamental disciplines. At that time I also participated under my thesis advisor Marcello Conversi to new instrumentation developments and to the realization of the first pulsed gas particle detectors.

Soon after my degree, in 1958 I went to the United States to enlarge my experience and to familiarize myself with particle accelerators. I spent about one and a half years at Columbia University. Together with W. Baker, we measured at the Nevis Syncro-cyclotron the angular asymmetry in the capture of polarized muons, demonstrating the presence of parity violation in this fundamental process. This was his first of a long series of experiments on Weak Interactions, which ever since has become my main field of interest. Of course at that time it would have been quite unthinkable for me to imagine to be one day amongst the people discovering the quanta of the weak field!

Around 1960 I moved back to Europe, attracted by the newly founded European Organization for Nuclear Research, where for the first time the idea of a joint European effort in a field of pure Science was to be tried in practice. The Syncro-cyclotron at CERN had a performance significantly superior to the one of the machine in Nevis and we succeeded in a number of very exciting experiments on the structure of weak interactions, amongst which I would like to mention the discovery of the beta decay process of the positive pion, p⁺ = p⁰ + e + v and the first observation of the muon capture by free hydrogen, µ^-+ p = n + v.

In the early sixties John Adams brought to operation the CERN Proton Syncrotron. I moved to the larger machine where I continued to do some weak interaction experiments, like for instance the determination of the parity violation in the beta decay of the lambda hyperon.

During the summer of 1964 Fitch and Cronin announced the discovery of CP violation. This has been for me a tremendously important result and I abandoned all current work to start a long series of observations on CP violation in K⁰ decay and on the K_L-K_S mass difference. Unfortunately the subject did not turn out to be as prolific as in the case of the previous discovery of parity violation and even today, some thirty years afterwards we do not know much more about the origin of CP-violation than right after the announcement of the discovery.

I returned again to more orthodox weak interactions a few years later, when together with David Cline and Alfred Mann we proposed a major neutrino experiment at the newly started US laboratory of Fermilab. The operational problems associated with a limping accelerator and a new laboratory made very difficult, albeit impossible for us during the Summer of 1973 to settle definitively the question of the existence of neutral currents in neutrino interactions, when competing with the much more advanced instrumentation of Gargamelle at CERN. Instead, about one year later we could cleanly observe the presence of all-muons events in neutrino interactions and to confirm in this way one of the crucial predictions of the GIM mechanism, hinting at the existence of charm, glamorously settled only few months later with the observation of the Y/J particle.

In the meantime and under the impulse of Vicky Weisskopf a new, fascinating adventure had just started at CERN with a new type of colliding beams machine, the Intersecting Storage Rings, in which counter-rotating beams of protons collide against each other. This novel technique offered a much more efficient use of the accelerator energy than the traditional method of collisions against a fixed target. From the very first operation of this new type of accelerator, I have participated to a long series of experiments. They have been crucial to perfect the detection techniques with colliding beams of protons and antiprotons needed later on for the discovery of the Intermediate Bosons.

By that time it was quite clear that Unified Theories of the type SU(2) x U(1) had a very good chance of predicting the existence and the masses of the triplet of intermediate vector bosons. The problem of course was the one of finding a practical way of discovering them. To achieve energies high enough to create the intermediate vector bosons (roughly 100 times as heavy as the proton) together with David Cline and Peter Mc Intyre we proposed in 1976 a radically new approach. Along the lines discussed about ten years earlier by the Russian physicist Budker, we suggested to transform an existing high energy accelerator in a colliding beam device in which a beam of protons and of antiprotons, their antimatter twins, are counter-rotating and colliding head-on. To this effect we had to develop a number of techniques for creating antiprotons, confining them in a concentrated beam and colliding them with an intense proton beam. These techniques were developed at CERN with the help of many people and in particular of Guido Petrucci, Jacques Gareyte and Simon van der Meer.

In view of the size and of the complexity of the detector, physics experiments at the proton-antiproton collider have required rather unusual techniques. Equally unusual has been the number and variety of different talents needed to reach the goal of observing the W and Z particles. International cooperation between many people from very different countries has been proven to be a very successful way of achieving such goals.

From Nobel Lectures, Physics 1981-1990, Editor-in-Charge Tore Frängsmyr, Editor Gösta Ekspång, World Scientific Publishing Co., Singapore, 1993

This autobiography/biography was first published in the book series Les Prix Nobel. It was later edited and republished in Nobel Lectures. To cite this document, always state the source as shown above.

Addendum, 1991

For eighteen years, I have dedicated one semester per year to teaching at Harvard University in Cambridge, Mass., where I have been appointed professor in 1970, spending the rest of my time mostly in Geneva, where I was conducting various experiments, especially the UA-1 Collaboration at the proton-antiproton collider until 1988.

On 17 December 1987, the Council of CERN decided to appoint me Director-General of the Organization as from 1st January 1989, for a mandate of five years.

My wife, Marisa, teaches Physics at High School, and we have two children, a married daughter Laura, medical doctor, and a son, André, student in high energy physics.

Autobiography: Simon van der Meer

I was born in 1925, in The Hague, the Netherlands, as the third child of Pieter van der Meer and Jetske Groeneveld, both of Frisian origin. I had three sisters.

My father was a schoolteacher and my mother came from a teacher's family. Under these conditions it is not astonishing that learning was highly prized; in fact, my parents made sacrifices to be able to give their children a good education.

I visited the Gymnasium in The Hague and passed my final examination (in the sciences section) in 1943. Because the Dutch universities had just been closed at that time under the German occupation, I spent the next two years attending the humanities section of the Gymnasium. Meanwhile, my interest in physics and technology had been growing; I dabbled in electronics, equipped the parental home with various gadgets and assisted my brilliant and inspiring physics teacher (U.Ph. Lely) with the preparation of numerous demonstrations.

From 1945 onwards, I studied "Technical Physics" at the University of Technology, Delft, where I specialized in measurement and regulation technology under C.J.D.M. Verhagen. The physics taught in this newly created subsection of an old and established engineering school, although of excellent quality, was of necessity somewhat restricted and I have often felt regrets at not having had the intensive physics training that many of my colleagues enjoyed. Nevertheless, if I have at times been able to make original contributions in the accelerator field, I cannot help feeling that to a certain extent my slightly amateur approach in physics, combined with much practical experience, was an asset.

After obtaining my engineering degree in 1952, I worked in the Philips Research Laboratory, Eindhoven, mainly on high-voltage equipment and electronics for electron microscopes. In 1956 I moved to Geneva to join the recently founded European Organization for Nuclear Research (CERN), where I have been working ever since on many different projects, in an agreeable and stimulating international atmosphere.

To start with, my work (under the leadership of J.B. Adams and C.A. Ramm) was concerned mainly with technical design: poleface windings, multipole correction lenses for the 28 GeV synchrotron and their power supplies. My interest in matters more directly concerned with the handling of particles was growing, in the meantime, stimulated by many contacts with people understanding accelerators. After working for a year on a separated antiproton beam (1960), I proposed a high-current, pulsed focusing device ("horn") aimed at increasing the intensity of a beam of neutrinos, then at the centre of interest at CERN and elsewhere. The design of this monster, together with the associated neutrino flux calculations kept me busy until 1965, when I joined a small group, led by F.J.M. Farley, preparing the second "g-2" experiment for measuring the anomalous magnetic moment of the muon. I designed the small storage ring used and participated at all stages of the experiment proper, including part of the data treatment. This was an invaluable experience; not only did I learn the principles of accelerator design, but I also got acquainted with the lifestyle and way of thinking of experimental high-energy physicists.

From 1967 to 1976 I returned to more technical work when I was responsible for the magnet power supplies, first of the Intersecting Storage Rings (ISR) and then of the 400 GeV synchrotron (SPS). I kept up with accelerator ideas, however, and worked (during my ISR period) on a method for the luminosity calibration of storage rings and on stochastic cooling. The latter was, of course, aimed at increasing the ISR luminosity, but practical application seemed difficult at the time, mainly because the high beam intensity in the ISR would have made the cooling very slow. After developing a primitive theory (1968) I therefore did not pursue this subject. However, the work was taken up by others and in 1974 the first experiments were done in the ISR.

Accumulation of the needed antiprotons would clearly require cooling. At this time, my work on the SPS power supplies had just come to an end; I joined a study group on the pp project and an experimental team studying cooling in a small ring (ICE). The successful experiments in this ring and the work by Sacherer on theory and by Thorndahl on filter cooling showed that p accumulation by stochastic stacking was feasible. The collider project was approved and I became joint project leader with R. Billinge for the accumulator construction. Since then, I have worked with the group that commissioned and improved the ring and that is now preparing the construction of a second ring to increase the p stacking rate by an order of magnitude. As a spin-off from this work, I proposed the stochastic extraction method that is now used (in a much improved form) in the Low-Energy Antiproton Ring (LEAR).

In 1976, Cline, McIntyre, Mills, and Rubbia proposed to use the SPS or the Fermilab ring as a pp collider.

In the meantime, in 1966, while skiing with friends in the Swiss mountains, I met my wife-to-be Catharina M. Koopman and after a very brief interval we decided to marry. This was certainly one of the best decisions I ever made; my life has since been far more interesting and colourful. We have two children: Esther (1968) and Mathijs (1970).

(added in 1991):

In 1990 I retired from CERN.

Horzours Loeb Lecturer, Harvard University, 1981.
Duddell Metal, Institute of Physics, 1982.
Honorary Degree, Geneva University, 1983.
Honorary Degree, Amsterdam University, 1984.
Foreign Honorary Member, American Academy of Arts and Sciences, 1984.
Correspondent, Royal Netherlands Academy of Sciences, 1984.

Nobel Lecture: Carlo Rubbia

Experimental Observation of the Intermediate Vector Bosons W⁺, W^- and Z⁰

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