Large Hadron Collider Pauses Operations Ahead of Major Upgrade
The world's largest particle accelerator, the Large Hadron Collider (LHC) operated by CERN, has entered its scheduled winter shutdown following a record-breaking year for particle collisions. Located near Geneva at the border between Switzerland and France, the facility achieved a historic milestone in 2025 by surpassing 500 inverse femtobarns (fb-1) in integrated luminosity, equivalent to approximately 50 quadrillion particle collisions.
This achievement marks the conclusion of the LHC's third full operational run. In the upcoming year, the accelerator will operate only briefly before undergoing a significant, multi-year upgrade. The planned enhancements aim to substantially increase the number of particle collisions, further advancing research in particle physics.
Record Performance and Scientific AdvancementsCERN reported that all four major experiments connected to the LHC--ALICE, CMS, ATLAS, and LHCb--delivered highly efficient data collection, achieving an operational efficiency rate of over 90 percent. The 2025 run included several firsts, such as successfully conducting collision cycles involving protons with oxygen ions, oxygen with oxygen, and neon with neon. Preliminary analyses suggest these experiments may offer valuable insights into the properties of quark-gluon plasma, a state of matter believed to have existed shortly after the Big Bang.
The LHC's continuous advancements have contributed significantly to the field of particle physics, including the landmark detection of the Higgs boson, which confirmed a crucial aspect of the Standard Model of particle physics. Research at the LHC involves accelerating protons to extremely high energies and colliding them within a 27-kilometer underground ring, enabling scientists to observe and analyze the fundamental particles and forces that comprise the universe.
Upcoming High-Luminosity UpgradeThe LHC undergoes an annual shutdown during the winter months to reduce energy consumption, as its operations require substantial electrical power. In addition to these regular pauses, extended shutdowns are scheduled periodically to allow for technical upgrades and maintenance. The last major upgrade was completed in 2018, which enabled the collider to reach higher energy levels in subsequent runs.
The next significant phase for the LHC is the High-Luminosity Large Hadron Collider (HL-LHC) project. Scheduled to begin after the current operational cycle ends in June, this upgrade aims to increase the collider's luminosity by a factor of ten compared to its original design. This enhancement is expected to enable the production of up to 15 million Higgs bosons annually by the mid-2030s, compared to approximately three million in 2017. A successful initial test of the new systems has underscored both the progress made and the necessity of the planned improvements.
Implications for Particle PhysicsThe forthcoming upgrades are designed to provide researchers with unprecedented volumes of data, facilitating deeper investigations into the fundamental structure of matter and the origins of the universe. Scientists anticipate that the enhanced capabilities will allow for more detailed studies of rare particles and processes, potentially revealing new phenomena beyond the current understanding of physics.
As the LHC enters its next phase of development, the global scientific community remains focused on the discoveries and technological innovations that may result from the collider's expanded capabilities. The planned upgrades underscore CERN's ongoing commitment to advancing the frontiers of scientific knowledge and maintaining the LHC's position at the forefront of particle physics research.