The Digester

CERN confirms missing doubly charmed baryon Xicc+

Mar 17th 2026

The LHCb experiment at CERN has observed the Xicc+ particle, a baryon with two charm quarks, with greater than 7 sigma significance, resolving a long-standing 2002 mass discrepancy and giving fresh data to probe how the strong force binds heavy quarks.

  • LHCb has discovered the Xicc+ baryon, made of two charm quarks and one down quark.
  • The result has a statistical significance above 7 sigma, exceeding the standard discovery threshold.
  • Xicc+ was expected to live about six times shorter than its Xicc++ sibling, which made it harder to find.
  • The measured mass matches the Xicc++ partner and contradicts the lower-mass signal reported by SELEX in 2002, closing that 20-year anomaly.
  • The discovery was enabled by upgrades to the LHCb detector and one year of new data, and it provides new input for testing quantum chromodynamics predictions.

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