The Large Hadron Collider — the largest, most powerful machine humanity has ever built — has gone quiet. On 27 June 2026, the final proton beams of its third run circulated through the 27-kilometre ring beneath the Swiss–French border, and CERN switched the collider off. It now enters Long Shutdown 3, a roughly four-year overhaul that will rebuild it into the far more powerful High-Luminosity LHC, with beams not expected to return until 2030.
So the current state of the LHC, in one line: it isn't broken and it isn't finished — it's mid-transformation. This guide explains what the machine just accomplished, why it's been powered down, what the multi-year upgrade actually involves, and what physicists hope the rebuilt collider will finally reveal.
What Is the Large Hadron Collider?
The Large Hadron Collider (LHC) is a particle accelerator run by CERN, the European Organization for Nuclear Research, near Geneva. In a 27-kilometre circular tunnel about 100 metres underground, it accelerates two beams of protons to almost the speed of light and smashes them together. In those tiny, violent collisions, energy briefly converts into matter — recreating conditions that last existed a fraction of a second after the Big Bang — and giant detectors record the debris.
Its most famous achievement came on 4 July 2012, when the ATLAS and CMS experiments announced the discovery of the Higgs boson — the particle tied to the field that gives other particles their mass, and the last missing piece of the Standard Model of particle physics. That discovery is why the LHC matters: it lets physicists test, at the highest energies ever reached, our best theory of what everything is made of.
The Current State: The Machine Just Went Quiet
As of mid-2026, the LHC is not colliding particles. Its third data-taking period, Run 3, ran from 2022 until the final beams on 27 June 2026, and it was the most powerful yet — protons collided at a record energy of 13.6 trillion electronvolts (TeV). With Run 3 complete, the machine powered down at the end of June and formally entered Long Shutdown 3.
This is normal. The LHC's life alternates between multi-year runs of data-taking and shutdowns for maintenance and upgrades. What makes this shutdown different is its scale: it's not a tune-up, it's a rebuild.
What Run 3 Achieved
Before it stopped, Run 3 delivered a huge haul of data — and, combined with earlier runs, cemented the LHC as one of the most productive scientific instruments in history. A few highlights of what the machine has done:
- A record-breaking dataset. The ATLAS experiment alone recorded around 505 inverse femtobarns of proton–proton collision data over its lifetime — a measure of total collisions — with about 332 of that collected during Run 3.
- More than 85 new particles. Across its runs, the LHC has discovered over 85 new hadrons — composite particles made of quarks — expanding the known particle "zoo."
- Sharper focus on the Higgs. Run 3 let physicists study rare Higgs behaviour, including new evidence for the Higgs boson decaying into a pair of muons and tighter measurements of how Higgs bosons interact with each other — subtle tests that could expose cracks in the Standard Model.
- Antimatter and the primordial soup. The LHC has probed why the universe is made of matter rather than antimatter, and recreated the quark–gluon plasma, the ultra-hot state of matter thought to have filled the early universe.
None of this was the "new physics" bombshell some hoped for — no dark matter particle, no supersymmetry. Instead, Run 3 tightened the picture, and set up the precision hunt to come.
What Is Long Shutdown 3?
Long Shutdown 3 (LS3) is the reason the collider is dark. Over roughly four years, CERN will carry out the most extensive intervention on its accelerator complex since the LHC was first built. Around 1.2 kilometres of magnets and associated components in the main tunnel will be removed and replaced with new, more capable equipment.
The accelerator chain is expected to gradually restart from around 2028, with the fully upgraded machine — the High-Luminosity LHC — scheduled to begin operations in 2030. In the meantime, the four big experiments are being overhauled too, fitting new detector components to cope with the far harsher collision environment ahead.
The High-Luminosity LHC: Ten Times the Data
The goal of all this work is luminosity — essentially, how many collisions the machine produces. The High-Luminosity LHC (HL-LHC) is designed to boost the collider's luminosity by up to a factor of ten beyond its original design. More collisions mean more chances to catch the rare, fleeting events that could reveal something new.
Here's the shift in scale:
| Run 3 LHC (until 2026) | High-Luminosity LHC (from 2030) | |
|---|---|---|
| Collisions per beam crossing | ~60 | 140–200 |
| Relative data rate | baseline | up to ~10× |
| Main goal | discovery + precision | precision at scale, rare-event hunt |
That jump comes at a price: cramming 140–200 collisions into every crossing (up from around 60) creates a data deluge and a much messier picture for detectors to untangle — which is exactly why the experiments need rebuilding during this shutdown.
Why Bother? What Physicists Hope to Find
The Standard Model is spectacularly successful, yet it's clearly incomplete — it says nothing about dark matter, offers no room for gravity, and can't fully explain why matter beat antimatter. Physicists suspect there are cracks in it, and the HL-LHC is built to find them by measuring known processes with extreme precision and searching for tiny deviations from prediction.
Top of the list is the Higgs boson itself. By 2030 the HL-LHC should collect enough data to measure how the Higgs interacts with itself — a property that probes the very shape of the field that fills the universe. Any surprise there, or in the rare decays now being studied, would be a signpost toward physics beyond the Standard Model. It's part of a bigger question we explore in is our model of the universe wrong? — and it connects to the fundamental nature of particles like the photon — the carrier of light that, as we explain in why light has no mass but still carries energy, the Higgs field tellingly leaves untouched.
What Comes After the HL-LHC?
Even as the HL-LHC is being built, CERN is looking further ahead. Physicists are studying a proposed successor — the Future Circular Collider (FCC), a ring roughly 91 kilometres around that would dwarf today's machine. It remains a proposal under feasibility study, with big decisions about cost and design still to come, and any such collider would be decades away. For now, the world's flagship for high-energy physics remains the LHC — and its most capable era is still ahead of it.
The Bottom Line
The Large Hadron Collider hasn't ended — it's being reborn. Run 3 closed in June 2026 after colliding protons at a record 13.6 TeV, and the machine is now in Long Shutdown 3, a four-year rebuild that will replace over a kilometre of magnets and transform it into the High-Luminosity LHC. When beams return around 2030, the collider will produce up to ten times more collisions, giving physicists their best-ever shot at precision-testing the Standard Model and catching a glimpse of whatever lies beyond it. The quietest period in the LHC's recent history is, paradoxically, the run-up to its most ambitious one. For more on the physics it's chasing, explore our physics hub.
Frequently Asked Questions
Is the Large Hadron Collider still running in 2026?
No — not at the moment. The LHC finished its third data-taking run when the final proton beams circulated on 27 June 2026, and it then entered a planned multi-year upgrade period called Long Shutdown 3. During this time it is switched off and not colliding particles. The machine is expected to gradually restart from around 2028, with the fully upgraded High-Luminosity LHC beginning operations in 2030. So the current pause is deliberate maintenance and rebuilding, not a fault or a shutdown for safety reasons.
What is the High-Luminosity LHC?
The High-Luminosity LHC (HL-LHC) is a major upgrade of the existing collider, being installed during the 2026–2030 shutdown. Its goal is to increase "luminosity" — the number of collisions the machine produces — by up to a factor of ten beyond the original design. More collisions give physicists far more chances to observe rare events. In practice, each beam crossing will produce 140 to 200 collisions, up from around 60. That flood of data should sharpen measurements of the Higgs boson and improve the odds of spotting new physics.
What did the Large Hadron Collider discover?
Its landmark discovery was the Higgs boson, announced on 4 July 2012, which completed the Standard Model of particle physics. Beyond that, the LHC has discovered more than 85 new hadrons — composite particles made of quarks — studied the imbalance between matter and antimatter, and recreated the quark–gluon plasma that filled the early universe. It has also placed strict limits on hypothetical new particles. Rather than a single bombshell, much of its value has come from precisely testing our best theory of matter at record energies.
Why is the LHC being shut down for four years?
The 2026–2030 shutdown, called Long Shutdown 3, is needed to physically rebuild large parts of the machine — the most extensive work on CERN's accelerators since the LHC was built. Around 1.2 kilometres of magnets and components in the tunnel are being removed and replaced with more powerful equipment, and the giant detector experiments are being upgraded to handle a much harsher collision environment. Work on this scale simply can't be done while the machine is running, so a long, planned pause is the only way to deliver the High-Luminosity upgrade.
How powerful is the Large Hadron Collider?
In its most recent run, the LHC collided protons at a record energy of 13.6 trillion electronvolts (13.6 TeV). To reach that, it accelerates protons to about 99.9999991% of the speed of light using 1,232 superconducting magnets chilled to around −271°C — colder than outer space. The collisions themselves are tiny, but concentrating that much energy into such a small point lets the machine briefly recreate conditions from just after the Big Bang, which is what makes new particles like the Higgs boson appear.
What will replace the Large Hadron Collider?
For now, nothing — the LHC's own upgrade, the High-Luminosity LHC, will keep it at the frontier of physics into the late 2030s. Looking further ahead, CERN is studying a proposed successor called the Future Circular Collider, a ring roughly 91 kilometres around that would be far more powerful than today's machine. However, it is still only a proposal under feasibility study, with major decisions on cost and design outstanding, and it would not come online for decades if approved.
