This Friday around 12 p.m., "two beams of protons (particles from the nucleus of the atom, editor's note) circulated in opposite directions along the 27-kilometer ring" of the Large Hadron Collider (LHC), announced CERN ( European Organization for Nuclear Research) in a press release.
Buried 100 meters underground on the Franco-Swiss border, the gigantic ring had been in technical stoppage since December 2018 for maintenance and improvement work, in the second longest break in its history.
The experiments at the LHC, started in 2008, notably led to the revolutionary discovery of the Higgs boson, the keystone of the fundamental structure of matter.
The recovery will take place gradually: a small number of protons have circulated for the moment in the two beams, at 450 billion electron volts (450 gigaelectron volts - GeV), a low collision rate but which will increase in power.
"The high-intensity, high-energy collisions will occur in a few months," said Rhodri Jones, head of CERN's beams department, welcoming a "successful" restart.
The principle of the collider is to collide particles at colossal speeds to generate elementary particles, infinitely small.
As the machine returns to service, the teams will increase the energy and intensity of the beams, to conduct collision experiments with a record energy of 13.6 trillion electronvolts (13.6 teraelectronvolts - TeV).
This will allow the four main LHC detectors (ALICE, ATLAS, CMS and LHCb) to receive more particle collisions and therefore to read a much larger mass of data.
CERN physicists will be able to "study the Higgs boson in great detail" and further test the standard model of particle physics, recently shaken by several experiments.
But the new phase of exploration aims above all to establish new physics beyond this model.
With perhaps new particles in the long term, such as supersymmetric particles: predicted by theory but never demonstrated, they could convey dark matter, a great unknown in the Universe.
© 2022 AFP