Somewhere beneath the rolling farmland of the Swiss-French border, 100 metres underground, protons are being hurled at one another at close to the speed of light. And in March 2026, one of those collisions produced something remarkable: the 80th particle ever discovered at CERN's Large Hadron Collider.
Its name is Xi-cc-plus. It lived for less than a trillionth of a second. And it could change our understanding of the force that holds every atom in the universe together.
A heavier cousin of the proton
To understand why physicists are excited, it helps to know what sits at the heart of every atom you have ever touched, breathed, or been made of. Protons — the positively charged particles inside atomic nuclei — are built from smaller building blocks called quarks. A regular proton contains two "up" quarks and one "down" quark, bound together by something called the strong nuclear force.
Think of the strong force as the universe's most powerful glue. It is what stops atomic nuclei from flying apart — and, strangely, it behaves like a rubber band, getting stronger the further you try to pull quarks away from each other.
Xi-cc-plus is essentially the proton's heavier cousin. It swaps those two up quarks for charm quarks — heavier, more exotic relatives — making it roughly four times the mass of a normal proton. It appeared briefly in a shower of debris from a proton collision at the LHCb experiment, before decaying into lighter particles in a flash too fast for human comprehension.
"The more we learn about these particles, the more we can learn about the strong force, and that is the same strong force that binds our protons and neutrons together," said Professor Chris Parkes of the University of Manchester, who led the international collaboration during the detector upgrade that made the discovery possible.
Twenty years of searching
Scientists had predicted Xi-cc-plus would exist for more than two decades. An experiment at Fermilab in the United States once claimed to have spotted it, but the result was never confirmed. The mystery lingered.
What finally cracked it was a major upgrade to the LHCb detector — a piece of technology so sensitive it takes 40 million "photographs" of particle collisions every second. In just one year of data from the upgraded machine, researchers found a clear signal of 915 Xi-cc-plus events, at exactly the mass their theories predicted.
"The improved detection capability allowed us to find the particle after only one year, while we could not see it in a decade of data collected with the original LHCb detector," said Professor Tim Gershon of the University of Warwick, who takes over as LHCb's international lead in July.
Glasgow's place at the frontier
The University of Glasgow is one of CERN's key partner institutions, with physicists contributing to both the ATLAS and LHCb experiments. The Glasgow LHCb group, led by Dr Lucia Grillo, builds and maintains critical components of the detector — including parts of the Vertex Locator that tracks particle paths with extraordinary precision, and the Ring Imaging Cherenkov system used to identify different types of particle.
Glasgow's researchers are now turning their attention to LHCb Upgrade 2, the next phase of improvements designed to hunt for even rarer particles. "We now eagerly await the incredible precision of results from Run 3 data and beyond," Dr Grillo said.
What comes next
CERN is already planning something even more ambitious: the Future Circular Collider. Where the current LHC occupies a 27-kilometre tunnel, the FCC would stretch to nearly 91 kilometres. Its first phase, an electron-positron collider, could begin operation in the late 2040s, with a proton collider reaching energies seven times greater than today's machine following in the 2070s. A decision by CERN's member states is expected in 2028.
The goal is to probe even deeper into the architecture of reality — hunting for particles we cannot yet imagine and testing whether our best theories of nature hold up under the most extreme conditions ever created by human hands.
A month for the history books
March 2026 has been a remarkable month for science. Alongside the Xi-cc-plus discovery, researchers solved a 50-year mystery about magnetism in Apollo moon rocks, and breakthroughs across astronomy and physics have rewritten what we thought we knew.
It is a reminder that for all the noise of daily life, humanity's most extraordinary project continues quietly underground: the patient, painstaking attempt to answer the simplest and most profound question of all — what is everything made of?
