Alfonso Albero, AlejandroBadalov, AlexeyCalvo Gómez, MíriamCamboni, AlessandroCoquereau, SamuelFernandez, G.Garrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniMarin Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséSánchez Gonzalo, DavidVilasis-Cardona, XavierLHCb Collaboration2019-05-032019-05-032017-09-110031-9007https://hdl.handle.net/2445/132664A highly significant structure is observed in the Λc+K-π+π+ mass spectrum, where the Λc+ baryon is reconstructed in the decay mode p K-π+. The structure is consistent with originating from a weakly decaying particle, identified as the doubly charmed baryon Ξcc ++. The difference between the masses of the Ξcc ++ and Λc+ states is measured to be 1334.94 ±0.72 (stat.) ±0.27 (syst. ) MeV /c2 , and the Ξcc ++ mass is then determined to be 3621.40 ±0.72 (stat.) ±0.27 (syst. ) ±0.14 (Λc+) MeV /c2 , where the last uncertainty is due to the limited knowledge of the Λc+ mass. The state is observed in a sample of proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.7 fb-1, and confirmed in an additional sample of data collected at 8 TeV.10 p.application/pdfengcc by (c) CERN; LHCb Collaboration, 2017http://creativecommons.org/licenses/by/3.0/es/Física de partículesExperimentsParticle physicsExperimentsinfo:eu-repo/semantics/article6780172019-05-03info:eu-repo/semantics/openAccess