Comerma Montells, AlbertGarcia Moreno, PaulaGarrido Beltrán, LluísGioventù, AlessandraGironella Gironell, PereGomez Fernandez, SergioGraugés Pous, EugeniLobo Salvia, AniolLópez Huertas, AlbertManera Escalero, RafelMarin Benito, CarlaMauricio Ferre, JoanCalefice, LukasVazquez Gomez, RicardoLHCb Collaboration2025-06-272025-06-2720241126-6708https://hdl.handle.net/2445/221849 The Λ 0 b → D+D−Λ decay is observed for the frst time using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.3 fb−1 . Using the B0 → D+D−K0 S decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be R = σΛ0 b σB0 × B(Λ0 b → D+D−Λ) B(B0 → D+D−K0 S ) = 0.179 ± 0.022 ± 0.014 , where the frst uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel, B(B0 → D+D−K0 S ), and the cross-section ratio, σΛ0 b /σB0 , previously measured by LHCb are used to derive the branching fraction of the Λ 0 b → D+D−Λ decay B(Λ0 b → D+D−Λ) = (1.24 ± 0.15 ± 0.10 ± 0.28 ± 0.11) × 10−4 , where the third and fourth contributions are due to uncertainties of B(B0 → D+D−K0 S ) and σΛ0 b /σB0 , respectively. Inspection of the D+Λ and D+D− invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The Λ 0 b → D∗+D−Λ decay is also observed for the frst time as a partially reconstructed component in the D+D−Λ invariant mass spectrum. 22 p.application/pdfengcc-by (c) Aaij, R. et al., 2024http://creativecommons.org/licenses/by/4.0/HadronsFísica de partículesGran Col·lisionador d'HadronsHadronsParticle physicsLarge Hadron Collider (France and Switzerland)info:eu-repo/semantics/article7564682025-06-27info:eu-repo/semantics/openAccess