The Large Hadron Collider Falls Silent — Inside the $1.5 Billion Upgrade That Will Reshape Physics

On June 29, 2026, operators at CERN's Control Centre dumped the final proton beams of the Large Hadron Collider, bringing more than 16 years of collisions to a deliberate end. The world's most powerful particle accelerator has fallen silent — and it will not wake up for four years.

The LHC is entering Long Shutdown 3 (LS3), the most ambitious upgrade campaign in CERN's history. When it restarts in 2030, it will no longer be the LHC as we know it. It will become the High-Luminosity LHC (HiLumi LHC), a machine capable of producing ten times more collisions than the original design, transforming the frontier of fundamental physics.

What the LHC achieved

Since circulating its first beams in September 2008, the LHC delivered discoveries that changed how we understand the universe. Its most famous moment came on July 4, 2012, when the ATLAS and CMS collaborations announced the discovery of the Higgs boson — the particle that gives mass to all other fundamental particles, and the last missing piece of the Standard Model. Beyond the Higgs, the collider discovered more than 85 new hadrons, probed the imbalance between matter and antimatter, explored the quark-gluon plasma that filled the early universe, and set the strongest limits yet on dark matter candidates and extra dimensions.

The engineering challenge ahead

LS3 involves far more than a routine maintenance stop. In the LHC tunnel alone, 1.2 kilometers of magnets and components will be dismantled and replaced with new equipment. The upgrade requires thousands of specialists from CERN and partner institutes worldwide, working across dozens of parallel projects.

The ATLAS and CMS detectors will be effectively rebuilt from scratch. They will need to handle between 140 and 200 proton-proton collisions per bunch crossing — compared to around 60 during the last run. That means identifying the most interesting events from more than five billion interactions every second. To meet this challenge, both experiments will install entirely new trigger systems, all-silicon tracking detectors with billions of readout channels, and timing detectors with precision measured in picoseconds.

What comes next

The HiLumi LHC will collect vastly larger datasets, enabling precision measurements of the Higgs boson that could reveal cracks in the Standard Model. With more collisions, physicists gain the statistical power to see rare processes that may point toward new physics — supersymmetry, dark matter candidates, or entirely unknown forces of nature.

While no beams circulate, CERN's scientific output continues. Thousands of researchers are still analyzing the petabytes of data accumulated during Runs 1 through 3, extracting new results that will be published throughout the shutdown period. The accelerator complex will begin a gradual restart from 2028 onwards, with the full HiLumi LHC expected to begin operations in 2030.

For nearly two decades, the LHC has been the sharpest instrument humanity has ever built for exploring the smallest building blocks of reality. Its silence is temporary — and when it returns, it will be more powerful than ever.