Observation of the doubly-charmed-baryon decay Ξ cc + + → Ξ c 0 π + π +

Abstract

A search for the doubly-charmed-baryon decay Ξ cc + + → Ξ c 0 π + π + is performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 5.4 fb−1. A significant structure consistent with the Ξ cc + + baryon is observed in the Ξ c 0 π + π + invariant-mass spectrum. Using the Ξ cc + + → Λ c + K − π + π + decay as the normalisation channel, the branching fraction ratio, B Ξ cc + + → Ξ c 0 π + π + B Ξ cc + + → Λ c + K − π + π + , is measured to be 1.37 ± 0.18 (stat) ± 0.09 (syst) ± 0.35 (ext). This measurement provides critical input for testing QCD factorisation methods in the weak decays of doubly-heavy baryons, particularly in quantifying nonperturbative effects such as final-state interactions and resonance contributions to the hadronisation process.