Physics using future high-energy accelerators

At the first meeting of the European Committee for Future Accelerators (ECFA), held last January [1963] at CERN, Prof L Van Hove presented a paper with the rather impressive title of "The physics that could be done with future high-energy accelerators as it appears in January 1963". This is a revised version of that talk.

The first thing to be said in an article of this kind is that it is not really possible to discuss the kind of physics experiments that may be done with high-energy accelerators in the future, simply because it is impossible to predict what new discoveries are likely to be made. All that can be done is to consider what experiments physicists would like to do with such machines, assuming nothing unexpected happens between now and the date they come into operation...

The physics of leptons

In the field of leptons, that is electrons, muons and neutrinos, as well as their interactions, which are the electromagnetic and the weak interactions, the last two years have not given any unexpected surprises. The discovery of the second neutrino, fundamental as it is, was not really a surprise but the confirmation of a bold theoretical prediction that a number of people had made on the basis of previously known facts. This lack of surprise is an indication that our understanding of this part of physics is much better, so that useful, realistic theoretical discussions are possible before experiments are done.

The most important task for a future programme of lepton physics is the search for deviations from the presently accepted theories of quantum electrodynamics and weak interactions. Both kinds of study are in progress now and will continue for quite a while. The extension of this sort of work will carry us necessarily to increasing momentum transfers, especially in electrodynamics. It will be necessary to do electron collisions (electron-electron and electron-proton) and muon-proton collisions at increasing energies and angles in order to explore the higher momentum transfers, which unfortunately have very small cross-sections.

The same general course will probably be followed with neutrino physics. Electron-nucleon scattering will be replaced by neutrino-nucleon collisions, and the main difficulty will be with the small cross-sections. Neutrino physics again has a possible fundamental discovery on the programme: the intermediate boson, which, if it exists, would fit well within the framework of current thinking. This type of work will no doubt be going on next year, the year after, and probably still in 1968 or 1970, although in the meantime unexpected things may come in addition - perhaps related to the strange particles, the weak decays of which are so puzzling.

The search for deviations from accepted theoretical views may give the answer to an outstanding question first asked long ago. This is the puzzle of the two electrons, the difference between electron and muon. It is not clear whether higher energy is necessarily needed in this case. Maybe the measurement of the mass of the neutretto, the neutrino of the muon, will produce a crucial advance. However, it may also be that to obtain new information on the electron-muon puzzle, neutrino energies of several hundred GeV would be required, which would be very expensive.
•Taken from CERN Courier April 1963 pp48-51.

Last month on the PS at CERN

During the whole of March [1963] work continued at the Proton Synchrotron on the numerous jobs arranged for the shut-down period. Of particular importance was the installation of the fast-ejection system, which will enable the beam of accelerated protons to be extracted from the machine, and the final setting-up apparatus for the forthcoming experiments with neutrinos...

The magnetic (or neutrino) horn was one of the first pieces of new equipment to be placed in position near the synchrotron during the shut-down. Seen in the picture above is Roger Gerst, working on the pulsed beam-transport system. This conducts the protons ejected from the accelerator to the target in the throat of the horn, where they produce pions.
•Taken from CERN Courier April 1963 p46 and p50.

Editor's note

ECFA, the European Committee for Future Accelerators, held its first ever meeting at CERN in 1963, and in the public session Léon Van Hove, then leader of the Theory Division, gave his view of the future, including his thoughts on neutrinos, which are extracted here. Van Hove became director-general of CERN from 1976-1980 and experiments with high-energy neutrinos became an important part of CERN's physics programme. Neutrinos remain a hot topic, and there are now ingenious new ideas for creating intense beams.