CERN's Upgraded Large Hadron Collider Makes Its First New Particle Discovery

Scientists led by the University of Manchester have identified a new, heavy doubly-charmed relative of the proton. This discovery was thanks to the use of the upgraded Large Hadron Collider at CERN (European Organization for Nuclear Research) and confirms a 20-year old claimed (but unconfirmed) observation of the same particle.

Deep beneath the border of France and Switzerland, the newly upgraded LHCb detector at CERN has captured a signal that physicists have hunted for decades. The particle, designated Ξcc⁺ (pronounced "Xi-cc-plus", a.k.a. Elon Musk's name of choice of his next child), was announced this week at the Rencontres de Moriond conference, and while it belongs to the same baryon family as the common proton, it is roughly four times heavier.
This discovery is particularly significant because it's the first new particle identified since the LHCb detector underwent a massive, multi-year upgrade completed in 2023 (while also making Ξcc⁺ the 80th particle found by LHCb since it started operations). The improved silicon pixel detectors can now process collisions at an unprecedented rate, which in this case, has been a boon for the researchers as Ξcc⁺ is so unstable that it exists for only a fleeting moment before decaying into a cascade of lighter particles.

The observation also settles a long-standing scientific dispute. Over 20 years ago, an experiment known as SELEX claimed to have found this particle at a much lower mass, but no other laboratory could replicate the result. The new data from CERN confirms the particle exists at a mass of approximately 3620 MeV/c², aligning with theoretical predictions and its previously discovered twin, the Ξcc⁺⁺.

Moving forward, the Ξcc⁺ particle provides a test for quantum chromodynamics, the theory describing the strong force that binds quarks and gluons together. By observing how these heavy charm quarks interact, theorists can refine the mathematical models that explain everything from the birth of the universe to the stability of the atoms in our own bodies.