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Researchers using the upgraded LHCb (Large Hadron Collider beauty) detector report evidence for a new particle called the doubly charmed baryon Ω_cc^+. In plain terms, this is a short-lived particle made from quarks that contains two charm quarks. The experimenters saw a clear peak in their data that they identify as this particle.
The search used proton–proton collisions recorded in 2024 with a total data size described as 6.3 inverse femtobarns — a standard way physicists count how many collisions were examined. The collisions had a center-of-mass energy of 13.6 teraelectronvolts (TeV). The team looked for Ω_cc^+ by reconstructing events where it would decay into an Ω_c^0 baryon and a positively charged pion (π^+). The Ω_c^0 itself was built from tracks identified as a proton (p), two negatively charged kaons (K^-), and a positively charged pion (π^+).
In the mass spectrum formed from Ω_c^0 and π^+ candidates, the analysis found a peaking structure with a global significance of 8.7 standard deviations (8.7σ). In particle physics, a significance above 5σ is normally taken as strong evidence that a signal is real and not a random fluctuation. The observed structure is reported to be consistent with originating from a particle that decays via the weak force, so the authors identify it as the doubly charmed baryon Ω_cc^+.
The measured mass of the new state is 3725.9 MeV/c^2 (about 3.726 GeV/c^2). The paper gives four separate uncertainties on that number: ±1.0 MeV/c^2 (statistical, coming from the finite size of the data sample), ±0.2 MeV/c^2 (systematic, from measurement and analysis effects), ±0.4 MeV/c^2 (a contribution related to an unknown lifetime that can bias the selection), and ±0.6 MeV/c^2 (an “external” uncertainty coming from the limited precision in the known masses of related baryons used in the analysis).
Important caveats accompany this result. The reported mass depends in part on assumptions about how the selection procedure reacts to the unknown lifetime of Ω_cc^+, which introduces the third quoted uncertainty. Another contribution to the final uncertainty comes from previously measured masses of related particles (Ω_c^0, Ξ_c^+, and Ξ_cc^{++}). The observation comes from a specific decay channel and from the 2024 LHCb dataset described; confirming measurements in other channels and further study of properties such as the particle’s lifetime will be needed to build a fuller picture.