A Day at CERN. Gautier Depambour
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 and production of some of the magnets. In short, when we talk about contributions, it is difficult to give a completely simple answer!
Since you’re talking about the accelerator and its detectors... how much did the LHC and its four experiments cost?
- The LHC machine costs around 5 billion Swiss francs, material and personnel included. The detectors cost about 1.3 billion Swiss francs. In total, by adding the costs related to data processing, the overall cost can be estimated at 7 billion Swiss francs.”
| That is about 6.5 billion euros. It is said that tax fraud causes Europe to lose at least 1 trillion euros a year... so let’s not aim at the wrong target! |
“Finally, to conclude on the question of costs, could you tell us what CERN’s energy bill is?
- All right; wait, I’ll find the number in this little booklet... Here it is: if we assume that the LHC operates 270 days a year, the energy used is equivalent to the power consumed by a third of the canton of Geneva over a year, or about 1.2 terawatt hours. That’s about 50 million euros — not so surprising, considering the machine you run!”
| You can put it in perspective the next time you receive your electricity bill. |
“Now that we’ve gone through the costs, it’s time for THE crucial question that everyone asks... Are all these expenses worth it?
- I think there are three possible types of answers. First of all, there is the “philosophical” answer, in a sense: CERN is used to better understand the world in which we live. Humanity will never cease to ask itself questions about the functioning of the universe; its will to know is inexhaustible! In your opinion, why did the discovery of the Higgs boson have a significant impact on the public? Because people, even without perhaps fully understanding what it is, are aware that it is related both to the origin of the mass of particles and to that of the universe, so in a way to our own origin. However, to enable such discoveries, current research requires ever more efficient instruments, which can be developed only through international collaborations. This more than anything is what justifies the existence of an organization like CERN, which is international by nature...”
Arnaud Marsollier
| That is true: I personally understood at CERN the importance in particle physics of the proverb “unity is strength”! |
“... Then there is the economic argument: CERN makes possible technological developments that have tangible impacts on industry. Studies have shown that for every euro invested in CERN, the return is 2 to 3 euros for contributors, particularly for France and Switzerland. New countries regularly join the organization, and they do not do so for no reason: they understand very well that, when such complex instruments are manufactured at the cutting edge of current technology, the industry concerned is enabled