The European particle physics laboratory CERN plans to build an underground ring with a perimeter of 91 kilometers to house the Future Circular Collider (FCC), the largest and most powerful particle accelerator in the world. If its construction is approved, it will allow the study of particle collisions with a precision and energy level never achieved before, which could provide answers to some of the unsolved mysteries of the Universe, such as the nature of dark matter and dark energy. , or why there is more matter than antimatter.
The FCC will be located in a 200-meter-deep tunnel straddling France and Switzerland and part of its route will pass under Lake Geneva, next to Geneva, according to the first conclusions of the FCC Feasibility Report that CERN has made public. . Inside it, two beams of particles will circulate in opposite directions at speeds close to those of light. At four points of the ring, head-on collisions will be caused between the particles by guiding them with magnets.
The energy released in the collisions will light up new particles according to Einstein’s equation E = mc² (where E designates the energy; m, the mass of the particles that will be created; and c, the speed of light). Four huge detectors located at these four points on the route will record the results of the collisions in search of unknown particles and unexpected phenomena.
The construction will require an investment of about 15 billion Swiss francs (about 15.7 billion euros at the current exchange rate), reported Fabiola Gianotti, director general of CERN, at the press conference in which she presented the status of the project. By comparison, the James Webb Space Telescope cost $10 billion to build and launch.
The decision whether or not to build the FCC will be made around 2028 by the CERN Council, the organization’s highest governing body, in which its 23 member states are represented, including Spain. If eventually built, the FCC will take over in the 2040s from the current LHC particle accelerator, where the Higgs boson was discovered in 2012.
Although that discovery was a success that validated the Standard Model – the physical theory that explains all known particles and three of the four fundamental forces of the Universe – the LHC has not provided any other advance of similar importance since then.
These twelve years of drought are attributed to the fact that there do not seem to be new particles or new physical laws to discover at the energy levels reached by the LHC. With a perimeter of 27 kilometers – less than a third of the projected length for the FCC – the LHC can collide particles at maximum energies of 14 TeV (teraelectronvolts).
However, there should be something important to discover at higher energies, since the Standard Model is an incomplete theory of the Universe, reports Aurelio Juste, Icrea researcher at the Institut de Physics d’Altes Energies (IFAE) in Bellaterra, who works on the CERN LHC.
The Standard Model does not explain observations such as dark matter (which appears to exert a gravitational attraction like stars but is invisible), dark energy (which accelerates the expansion of the Universe with an effect apparently opposite to that of gravity) or supremacy of matter over antimatter (which explains why we are here, since matter and antimatter annihilate each other and, if they had been created in equal quantities after the big bang, galaxies, stars, planets and living beings could not have formed) .
According to the majority opinion in the particle physics community, going beyond the Standard Model will require a machine with performance superior to that of the LHC. The current accelerator, which entered service in 2010, is expected to continue operating until 2040, after several renovations that are progressively increasing its performance.
In anticipation of the end of the LHC, the CERN Council commissioned a Feasibility Study of the Future Circular Collider in 2020. The study must define the design, location and feasibility of the FCC. The first conclusions indicate that “there are no technical or scientific obstacles” that prevent carrying out the project, declared Eliezer Rabinovici, president of the CERN Council, at a press conference on February 5.
The work schedule foresees that the final report of the Feasibility Study will be presented in the first half of 2025 so that the CERN Council can make a decision on the construction of the FCC three years later. During this period, member states will be able to evaluate the project and its financing.
If its construction is approved, work would begin in the early 2030s and the accelerator would enter service in the mid-2040s. In a first phase, electrons and positrons (the antiparticles of electrons) would be collided, which They are ultralight particles, so enormous energies would not be achieved in collisions but very high precision would be achieved. In a second phase, starting in the 2070s, protons, which are much more massive, would be collided, reaching energies of 100 TeV, seven times higher than at the LHC.
This strategy of starting with very precise measurements and then exploring very energetic collisions in the same underground tunnel is the same one that CERN has successfully applied in the past with the LEP and LHC accelerators, points out Aurelio Juste, from the IFAE institute. “Precision tells us which is the correct direction in which we have to progress and which are the directions that we have to discard; Then, with proton collisions, we can find what we are looking for by applying brute force,” as was done with the Higgs boson, explains Juste.
The investment to build the FCC will come largely from CERN’s own general budget, contributed by the 23 member states, and “will be spread over ten or twelve years,” Gianotti reported. But the construction of the FCC, he advanced, “will need additional contributions,” which other countries could contribute. Talks have already begun with the US, whose scientists represent 16% of the CERN community, for future funding of the FCC.
