Ten years following its discovery of the Higgs boson, CERN’s LHC, the largest and most powerful particle accelerator in the world, will restart on Tuesday at record collision energy. The goal? Drill a little deeper into the secrets of matter.
The Large Hadron Collider (LHC) was restarted in April, following a technical shutdown of three years, for maintenance work and to improve its production and particle detection.
It will operate at its full collision power of 13.6 trillion electron volts (TeV) for four years, European Organization for Nuclear Research (CERN) officials announced in a press briefing last week. .
Its two beams of protons – the particles of the nucleus of the atom – accelerated to a speed close to that of light, will circulate in opposite directions in the ring of 27 km, buried 100 meters underground at the border Franco-Swiss.
The detectors of several experiments (in particular ATLAS, CMS, ALICE and LHCb), will then record the collisions of protons, which produce ephemeral particles explaining the functioning of matter.
1.6 billion collisions per second
“We are aiming for a rate of 1.6 billion proton-proton collisions per second for the ATLAS and CMS experiments,” said Mike Lamont, director of accelerators and technology at CERN, on Thursday.
The more violent these collisions, the more they make it possible to “break” the particles to identify their components and their interactions.
The proton beams will be concentrated to reach at the interaction points a microscopic size, “10 microns, in order to increase the rate of collisions” of protons, explained Mike Lamont.
The world temple of the infinitely small, built in 2008, led to the discovery of the Higgs boson, announced exactly ten years ago by Fabiola Gianotti, then coordinator of the ATLAS experiment and now Director General of CERN.
“The Higgs boson is linked to some of the deepest questions in fundamental physics, from the structure and shape of the Universe to how other particles organize themselves,” according to the researcher.
His discovery revolutionized physics, confirming the prediction of researchers who had made it, nearly 50 years earlier, a centerpiece of the Standard Model of particle physics (SM). The Higgs boson is the manifestation of a field, that is to say a space, which gives mass to elementary particles forming matter.
Still secrets to deliver
The researchers were able to flush it out thanks to the analysis of around 1.2 billion billion collisions of protons between them. The third run of the LHC which opens on Tuesday will multiply this figure by twenty. “This is a significant increase which opens the way to new discoveries”, notes Mike Lamont.
Because the Higgs boson has not given up all its secrets. Starting with its nature. “Is it a fundamental particle or a composite”, namely an assembly of several particles still unknown, questions Joachim Mnich, Director of Research and Calculation at CERN. Better, “is it the only existing Higgs particle or are there others?”
Past experiments have made it possible to determine the mass of the Higgs boson, and also to discover more than 60 composite particles predicted by the Standard Model, such as the tetraquark.
But as Gian Giudice, head of the theoretical physics department at CERN, reminds us, “particles are only the manifestation of a phenomenon”, whereas “the objective of particle physics is to understand the fundamental principles of nature “. Like the nature of the hypothetical dark matter or the no less mysterious dark energy.
Nine experiments will thus take advantage of the production of particles from the accelerator. Like ALICE, which studies the primordial plasma of matter that prevailed in the first ten microseconds following the Big Bang. Or LHCf, which simulates cosmic rays.
The next stage of the large collider will come following the third pause, in 2029, with its transition to “high luminosity”, which will multiply by ten the number of detectable events.
Beyond that, CERN researchers are looking towards the Future Circular Collider (FCC) project, a 100 km ring whose feasibility study is expected at the end of 2025. “It will be the ultimate machine for studying the Higgs boson, which is a very powerful tool for understanding fundamental physics,” concluded Fabiola Gianotti.
