Excellent. I have comprehensive research. Now let me write the article with an inverted pyramid journalistic structure, maintaining the proper style requirements (no first person, objective tone, no generic headers).
The Large Hadron Collider is shutting down—but not for good. The world's most powerful particle accelerator will cease operations this June and remain offline for approximately four years while engineers conduct the most ambitious upgrade in its history.
The hiatus marks a pivotal moment in particle physics, transforming the facility from a discovery engine into a precision instrument designed to unlock secrets about the universe's fundamental nature.
The shutdown, formally designated Long Shutdown 3 (LS3), officially commences on June 29, 2026, following the completion of the LHC's third operational run. This extended maintenance period will stretch through 2030, with operations resuming in June of that year.
The timing represents a seven-month delay from the originally planned December 2025 start date—a postponement driven by unforeseen complexities in upgrading the facility's twin flagship detectors, ATLAS and CMS, both of which have encountered significant technical challenges during their design and construction phases.
The reason for such an extended interruption underscores the magnitude of the undertaking. Engineers will install entirely new detector systems, replace thousands of components subjected to intense radiation, and deploy revolutionary new magnet technology designed to intensify particle collisions by a factor of ten.
This transformation, called the High-Luminosity LHC (HL-LHC) project, will enable roughly 15 million Higgs boson collisions annually by the mid-2030s—a stark contrast to the approximately three million produced in 2017. The accumulated data will balloon to unprecedented volumes, exceeding 4,000 inverse femtobarns of integrated luminosity at collision energies of 13.6 to 14 tera-electron volts.
The 2025 operational year provided an auspicious conclusion to the current phase. The LHC delivered a record-breaking 500 inverse femtobarns of integrated luminosity, surpassing all previous annual totals and completing the third full operational run with remarkable efficiency.
All four major experiments—ATLAS, CMS, ALICE, and LHCb—achieved operational efficiency exceeding 90 percent, generating vast datasets for analysis. The final year also witnessed historic milestones: for the first time, the facility successfully collided oxygen nuclei with oxygen nuclei, and neon with neon, producing observations of quark-gluon plasma under entirely new conditions.
Mark Thomson, who assumed the position of Director-General of CERN on January 1, 2026, enters his five-year mandate during this shutdown phase, a timing that might seem less than ideal. Yet Thomson has characterized the situation with evident enthusiasm. "It's an incredibly thrilling project," he stated in interviews regarding the upgrade.
"It's more engaging than merely watching the machine work continuously." Thomson, a veteran particle physicist from the University of Cambridge who previously served as executive chair of Britain's Science and Technology Facilities Council, brings extensive experience managing large-scale research infrastructure and has already begun coordinating the complex logistics of LS3.
The technical scope of the work rivals the construction of the LHC itself. Civil engineering crews will drill 28 vertical shafts connecting new underground technical galleries to the existing 27-kilometer tunnel. These galleries, totaling 1.5 kilometers of new underground construction, will house innovative cryogenic systems, superconducting crab cavities, and transmission lines cooled to near absolute zero. The civil engineering phase alone is expected to consume six months—double the original estimate—reflecting unforeseen geological challenges encountered during site surveys.
The ATLAS and CMS experiments require the most extensive modifications: entirely new silicon tracking detectors capable of withstanding radiation doses ten times greater than current systems, advanced timing detectors with nanosecond precision, and upgraded trigger systems that can process collision data at 40 megahertz, selecting only the most scientifically valuable events from the trillions that occur annually.
This upgrade promises transformative scientific potential. Higgs boson coupling measurements will achieve percent-level precision, roughly ten times more accurate than current capabilities. Such precision allows physicists to test whether the Higgs particle interacts with matter and forces exactly as the Standard Model predicts or whether deviations hint at undiscovered physics.
The HL-LHC will enable searches for rare processes, such as Higgs bosons decaying into pairs of muons, which occur so infrequently that only the massive dataset this upgrade provides will render them statistically significant. Measurements of the W boson mass, considered a fundamental constant of nature, will improve by an order of magnitude, contributing to tests of whether the universe remains stable at extremely high energies.
The delay in commencing LS3 reflects broader challenges facing large experimental physics in the 2020s. The COVID-19 pandemic interrupted supply chains and construction timelines. Russia's invasion of Ukraine disrupted international collaboration and access to specialized materials.
The complexity of modern detector technology, requiring innovations in silicon sensor manufacturing, cryogenic engineering, and real-time data processing, has pushed development schedules beyond initial projections. Some observers view these delays as symptomatic of the challenges facing increasingly ambitious physics projects.
Beyond the immediate upgrade, the LHC's ultimate fate has entered scientific discussion. CERN has identified 2041 as the planned end of the facility's operational life. However, the European particle physics community is actively developing proposals for a successor: the Future Circular Collider (FCC), a facility with a circumference of 56 miles—more than three times the LHC's 27-kilometer ring.
The FCC would operate in two phases, initially colliding electrons and positrons, then upgrading to proton-proton collisions at even higher energies. A feasibility study completed in March 2025 found no showstoppers to construction, though the estimated $19 billion price tag exceeds CERN's unilateral financial capacity and will require unprecedented international funding collaboration. The CERN Council is expected to render a decision on FCC construction around 2028, roughly during the HL-LHC upgrade's midpoint.
Scientists view the current shutdown not as a pause but as a necessary evolution. While detectors sit silent and magnets rest, theoretical physicists will analyze the mountains of data collected during Run 3, potentially identifying subtle patterns in collision events that hint at physics beyond the Standard Model.
The HL-LHC's enhanced capabilities will scrutinize phenomena that occur so rarely they have hitherto remained invisible—exotic decays of known particles, evidence of long-lived particles predicted by supersymmetric theories, and precision measurements that may reveal the universe operates according to principles not yet discovered. The 2030 resumption will commence a new era of particle physics where statistical power rather than collision energy drives discovery.
The shutdown represents confidence in particle physics' future at a moment when funding pressures and philosophical questions about whether ever-larger accelerators represent optimal investment have generated genuine debate.
CERN's decision to proceed reflects institutional conviction that the questions HL-LHC will address—the nature of the Higgs boson, the mystery of dark matter, the potential for new particles and forces—justify the commitment. When operations resume in mid-2030, the Large Hadron Collider will emerge as something fundamentally different: not the world's highest-energy laboratory, but the world's most precise instrument for studying the quantum realm.
