NarrativeTen years after the discovery of the Higgs boson, disconcerting observations are questioning physicists: are they artifacts or clues to the existence of particles and unprecedented forces?
It’s go again. And even several. At the European Organization for Nuclear Research, CERN, near Geneva (Switzerland), in the underground tubes 27 kilometers in circumference, the particles have been back, since April, within the LHC circular accelerator to collide and hope to reveal new secrets to physicists. But the atmosphere is less serene than a few years ago, when the hope was to make a major discovery, which finally took place in July 2012. In the midst of the collisions, the last particle that was missing from the hunting board, the Higgs or Brout-Englert-Higgs boson, according to the name of its “parents”.
“Everything was going well. After the Higgs, we expected other new particles predicted by the so-called “supersymmetric” theory, or SUSY, which promised to settle a lot of fundamental questions. It was the time of guaranteed discoveries », rewinds Christophe Grojean, physicist at the DESY research center in Germany. But the scenario did not come true. Since the Higgs, nothing that was predicted by SUSY has been found… No light particle that could have constituted dark matter, an unknown substance necessary for the cohesion of galaxies. No fireworks from newcomers that would have doubled the number of known particles. “And the big questions always remain openrecalls Christophe Grojean. We must therefore return to the basics: experience must be the engine of physics. »
Hence a renewed excitement, thanks to several experiments: the new start for the LHC and, above all, several intriguing results, at CERN or elsewhere. In one case, it is a particle that weighs heavier than expected. In another, it is a particle that does not turn very round. In a third, two members of the same family are bickering. In short, nothing is going right… but that’s good news. Indeed, all these small deviations, all these small deviations, all these anomalies make physicists think that this is perhaps as much evidence that the model, which until then worked so well, is showing its first signs. tired.
Anomalies as “compasses”
This model is the standard model: three forces, seventeen particles, everything is said. “The Standard Model has been put under incredible strain, but no one, so far, has been able to break it and its predictive power remains extremely strong”recalls Guido Tonelli, former spokesman for CMS, one of the two experiments that saw the Higgs boson. “It explains everything, radioactivity, fusion in stars, lasers, MRIs… It’s very precise”insists David Toback, spokesman for CDF, one of the experiments with the “abnormal” result.
You have 81.5% of this article left to read. The following is for subscribers only.