Researchers at CERN announced on 22 April 2022 that the Large Hadron Collider (LHC) has restarted after a three-year break for maintenance, consolidation, and upgrade work.
What has the Large Hadron Collider observed since it restarted?
On 22 April 2022, two beams of protons circulated in opposite directions around the LHC’s 27-kilometre ring at their injection energy of 450 billion electronvolts (450 GeV).
“These beams circulated at injection energy and contained a relatively small number of protons. High-intensity, high-energy collisions are a couple of months away,” explained Rhodri Jones, the Head of CERN’s Beams Department. “But first beams represent the successful restart of the LHC accelerator after all the hard work of the long shutdown.”
“The machines and facilities underwent major upgrades during the second long shutdown of CERN’s accelerator complex,” added Mike Lamont, CERN’s Director for Accelerators and Technology. “The LHC itself has undergone an extensive consolidation programme and will now operate at an even higher energy and – thanks to major improvements in the injector complex – it will deliver significantly more data to the upgraded LHC experiments.”
What do these beams mean for the particle accelerator?
CERN scientists observed that pilot beams circulated in the LHC for a brief period in October 2021. However, the beams that circulated on 22 April 2022 marked not only the end of the second long shutdown for the LHC, but also the beginning of preparations for four years of physics-data taking, which is expected to begin in the summer of 2022.
Until then, LHC experts intend to progressively recommission the machine and safely enhance both the energy and intensity of the beams, before delivering collisions to the experiments at a record energy of 13.6 trillion electronvolts (13.6 TeV).
What data do scientists intend to collect?
This third run of the LHC – known as Run 3 – will observe the machine’s experiments and will collect data from collisions, both at record energy, and also in unparalleled numbers.
Researchers expect that the ATLAS and CMS experiments will receive more collisions during this physics run than in the two previous physics runs combined, while the LHC, which underwent a complete revamp during the shutdown, can hope to see its collision count increase by a factor of three.
Meanwhile, ALICE, a specialised detector for studying heavy-ion collisions, can expect up to a fifty times increase in the total number of recorded ion collisions, due to the recent completion of a major upgrade.
What does this mean for science?
The unprecedented number of collisions detected by the LHC will allow international teams of physicists at CERN and across the world to study the Higgs boson in great detail and put the Standard Model of particle physics and its various extensions to the most stringent tests yet.
Other things to anticipate in Run 3 also include the operation of two new experiments:
- FASER and SND@LHC, which is designed to look for physics beyond the Standard Model;
- Special proton–helium collisions to measure how often the antimatter counterparts of protons are produced in these collisions; and
- Collisions involving oxygen ions that will improve physicists’ knowledge of cosmic-ray physics and the quark–gluon plasma, a state of matter that existed shortly after the Big Bang.
