CERN shuts down the LHC accelerator: the transition to High Luminosity begins

CERN has permanently shut down the Large Hadron Collider (LHC), the world's most powerful particle accelerator, initiating the technical shutdown period known as Long Shutdown 3 (LS3). During this phase, lasting several years, the 27-kilometer underground ring on the French-Swiss border will undergo a profound technological transformation to become the High Luminosity LHC (HL-LHC).

During LS3, 1.2 kilometers of magnets and components will be removed and replaced with new technologies. These modifications will allow the future accelerator to achieve a luminosity 10 times greater than the current LHC, generating up to 200 collisions per event compared to the previous approximately 60. The first beams of the HL-LHC are expected in 2028, with full operation commencing in 2030.

Research at CERN will not come to a complete halt: while no new proton beams will circulate, physicists will continue analyzing the enormous amount of data already collected in previous years, while simultaneously preparing new experiments for the next generation of high-intensity collisions.

The Large Hadron Collider (LHC) is the largest and most powerful particle accelerator ever built, located in a 27-km circular tunnel 100 meters underground at the border between France and Switzerland. Activated in 2008 after decades of design and construction, the LHC represented an unprecedented international scientific effort, involving thousands of researchers from around the world.

The accelerator revolutionized particle physics, enabling fundamental discoveries such as that of the Higgs boson in 2012—the particle that gives mass to all others. In the following years, the ATLAS and CMS experiments continued to study proton-proton collisions at increasingly higher energies, exploring the frontiers of fundamental physics and seeking answers about the nature of dark matter and matter-antimatter asymmetry.

The transition to the High Luminosity LHC represents the natural evolution of this instrument. The project arose from the need to drastically increase the number of collisions to study increasingly rare phenomena. This transition, planned for years, marks the culmination of a research cycle and opens a new chapter in experimental physics, with advanced technologies that will enable the exploration of previously inaccessible regions of fundamental physics.