a European laboratory for high-energy physics, with UNESCO’s support, which encouraged the creation of scientific collaborations without a military aspect. The idea was to bring together young researchers from all over Europe, to put them in contact with each other, then to send them back to their home universities with a high level of excellence and thus restore the reputation of basic science in Europe. Eleven countries agreed on the principle, but it was still necessary to decide where the new laboratory would be located.
One group of theorists made a strong argument for Copenhagen. This is where the iconic Niels Bohr Institute of Theoretical Physics was (and still is) located, an essential place in the advent of quantum mechanics, which witnessed an intense intellectual ferment in the 1920s and 1930s. Niels Bohr himself, still alive at the time, was involved in the creation of CERN.
There were other possible choices: France, Italy... But Switzerland, with its central position in Europe and its tradition of peace, was the ideal candidate. The question of location was settled in Amsterdam in 1952, at a conference where it was decided that the Laboratory would be located in Meyrin, in the open countryside near Geneva — a decision endorsed by a referendum in 1953 by which the local population accepted the project. And the following year, 12 countries signed the CERN Convention, officially recording its birth: Belgium, Denmark, France, Germany (in fact, the FRG), Greece, Italy, Norway, the Netherlands, the United Kingdom, Sweden, Switzerland and Yugoslavia. In parallel, the theoretical section of CERN, of which Niels Bohr was a member, was initially established in Copenhagen, but this did not last long, given the distance from Switzerland.
The first objective of the collaboration was to build particle accelerators to unlock the secrets of matter. Several circular accelerators thus emerged one after the other, each larger than the one before. In the 1950s, the Proton Synchrotron was built, which, among other things, allowed the study of very strange particles that we will have the opportunity to discuss again: neutrinos. About twenty years later, the Super Proton Synchrotron was born — from then on, the PS was converted into an SPS injector, so that the protons arriving in the SPS had already acquired a certain energy, as I explained earlier.
The SPS, which sent protons against antiprotons, had its moment of glory in 1983 by allowing the discovery of the Z0, W+ and W- bosons, which earned Carlo Rubbia and Simon van der Meer the Nobel Prize in 1984. These are the mediating particles of one of the four fundamental forces of nature: the weak nuclear force, involved in beta radioactivity processes. Today, the mass of the boson Z0 is known with great precision, and for this reason it acts as a standard when calibrating the detectors.
Proton collisions are conducive to the discovery of new particles; indeed, because they have a composite structure, they can produce a wide variety of collisions, allowing a wide range of energy to be explored and thus very different particles to be observed. On the other hand, when we want to study a known particle in a narrow and well-defined energy range, electron collisions (which, to our knowledge, do not have an internal structure) are more suitable because they are “cleaner.” Thus, after the discovery of the Z and W bosons, CERN decided to change its strategy by producing collisions no longer of protons, but of electrons, in order to study these new particles in detail. But when electrons circulate in an accelerator, they emit radiation called “synchrotron radiation” and lose energy because of this phenomenon. The same is true for protons, but in much smaller proportions: for the same energy, electrons lose about 10,000,000,000,000,000 times more energy than protons through synchrotron radiation. In short, it had become necessary again to build an accelerator even larger than the SPS.
This is what gave birth to the LEP, the Large Electron–Positron collider of 27 km of circumference powered by the SPS, which produced collisions between electrons and their antimaterial congeners (if I may say so), positrons. LEP made important discoveries, such as studying the decay of boson Z into other particles, in perfect accordance with the theoretical hypotheses formulated since the 1950s.
From the 1980s onwards, physicists decided to return to proton collisions, keeping the tunnel of the LEP but changing the accelerator inside. This led to the construction of the LHC, the Large Hadron Collider, in the place of the LEP. A hadron is a particle subjected to strong nuclear interaction, which ensures the cohesion of atomic nuclei, and this is the case of the components of the proton (quarks and gluons — we will come back to this later).
The LHC achieves such high energies that it recreates at the collision points the physical conditions that prevailed just after the Big Bang (in the case of collisions between lead ions). This is already remarkable, but we still hope to increase energy to highlight new particles, whether predicted or not by current theories.
Interview with Arnaud Marsollier
CERN funding
We have arrived at Arnaud’s office. You will finally have all the arguments you need to convince those around you who might wonder what CERN is for or what the point is of funding such an organization. Here it is, let me knock. I think I hear him coming...
“Hello, Arnaud, thank you for welcoming us to your office.
- Hello, both of you! Please, take a seat.
Bernard advised me to talk to you about CERN’s finances... So I would like, if you don’t mind, to talk first about how much CERN costs, and then explain why these investments are worth it. So let’s start with the expenses... A first simple question: how much does CERN cost per year?
- CERN costs about one billion Swiss francs per year...”
| A Swiss franc corresponds to a little bit less than one euro. |
“... Our General Manager would say that it is the equivalent of one cappuccino per European per year...”
| So I will ask you this question at the end of the visit: are you ready to offer a cappuccino to CERN every year? As for the General Manager, her name is Fabiola Gianotti. |
Fabiola Gianotti
“... This money comes from the annual contributions of the Member States, in proportion to their wealth. France, for example, contributes about 15% to the CERN budget, that is, about 150 million euros. Then, if CERN has to make major investments, it can benefit from a credit facility from the European Investment Bank. For example, for the LHC High Lumi...”
| The LHC High Lumi is the High Luminosity phase of the LHC planned for 2026 to 2037, in which the number of proton collisions will be multiplied by approximately 10. |
“... CERN will be able to get 250 million francs from this bank, which will then be repaid over several years. That’s not all: CERN is responsible for the accelerators like the LHC, but not for the detectors, and only funds part of the ATLAS, CMS, ALICE and LHCb experiments. These experiments are independently funded by their respective international collaborations, consisting of universities, laboratories, etc. For example, the French laboratories working on ATLAS partly finance the ATLAS experiment. These laboratories or universities do not necessarily belong to Member States. Thus, the largest community of CERN users is the Americans, while the United States is not a member state of CERN! So the Americans contributed directly to the experiments, and in the case of the accelerator, they were involved in the design
