Three or four theories are candidates to replace

Muon, gluons and leptons and electron resume service. The most powerful accelerator in the world between in action today at CERN () near Geneva. The LHC will start one of its two beams of protons, a tower of heater prelude several weeks rise in plan. If all goes well, particle production will begin in the fall. And, in the best cases, the LHC eventually revolutionize our vision of matter and the universe.

Not surprising, therefore, to CERN thousands of impatiently impatience and anxiety. This is more than ten years they build on this "toy" of EUR 6 billion to boost scientific discipline full question. "With the exception of the physical dynamics of the neutrino", nuance Daniel Fournier, researcher at the University of Orsay. The particle physics, it is a little sprint 100 meters of the science. It attracts the lights, stirs up fierce competition, but its progress is slow. Very productive in the first half of the 20th century, fundamental physics, has since raised more theoretical questions than it provided answers. Roy Aleksan, physicist at the CEA and Member, as Daniel Fournier, of the Scientific Council of CERN, recalled the chasm that defies its community: "We found that 5 of the matter in the universe."

Out of the blur, particle physicists are on the power of the LHC. Primary focus: the Higgs boson, the most sought-after particle in the scientific community. Without this key, it is all of the standard model that breaks down. Because, even before tackling for the 95 of unknown, physicists must lock the famous theory of the 20th century which explains 5 of the known matter.

The standard model summarizes the universe 12 particles (leptons and quarks) and 4 (high, low, gravitational, electromagnetic) forces. Quarks are the constituents of material and forces act through particles circulating between the particles of matter (see diagram). This theory has earned the trust of physicists for predicted phenomena then audited in accelerators. So, the model remains flawed until one of its pillars remains theoretical: the Higgs field and its associated particle, the boson. Through them, the researchers have succeeded in the 1960s to justify the force of gravitation. The standard model does not otherwise explain why some particles have mass. The Higgs field if: the particles which interact strongly with the same field are heavy, those who do not have no mass, such as the photon. Must take the boson on the go. "The particle physics is an experimental science, without observation, a theory is a theory," insists Roy Aleksan. But for the researcher, the discovery of the boson is a step before a more ambitious adventure: "the theory of the standard model works properly in the energy range up to 500 GeV (giga-electron-volts), or even 1 TeV (1,000 GeV). Beyond that, it is incomplete. Three or four theories are candidates to replace. "I hope that the LHC will be able to reveal what is good," says Roy Aleksan.

Mysterious particles

With its accelerator, CERN could begin to explore these famous 95 of the world ignored the standard model. First, there are the dark matter of the mysterious particles that interact with the known material. The probability of detection is very low, for still more intense accelerators. It also most powerful collisions to reveal these particles to large masses. As dark energy which would be two thirds of the universe, scientists know even less. It is presumed responsible for the acceleration of the expansion of the universe. Physicists competed imagination for ages to create seams between the standard model and the theory of general relativity which describes the universe high energy and large scales.

Today, some physicists consider even the existence of parallel universe. But the supersymmetry is currently the strongest theory. Its proponents propose to assign to each existing particle particle mirror. The lightest of them might constitute the dark matter. "If it is found at CERN, it's the jackpot", is dreaming Daniel Fournier.