Camboni, AlessandroCoquereau, S.Garrido Beltrán, LluísGascón Fora, DavidGraciani Diaz, RicardoGraugés Pous, EugeniMarin Benito, CarlaPicatoste Olloqui, EduardoRives Molina, Vicente JoséAlfonso Albero, AlejandroCalvo Gomez, M.Gironella Gironell, P.Vazquez Gomez, R.LHCb Collaboration2022-06-072022-06-072017-041126-6708https://hdl.handle.net/2445/186405The suppressed decay Λ b 0 → pπ - μ + μ -, excluding the J/ ψ and ψ(2 S) → μ + μ - resonances, is observed for the first time with a significance of 5.5 standard deviations. The analysis is performed with proton-proton collision data corresponding to an integrated luminosity of 3 fb-1 collected with the LHCb experiment. The Λ b 0 → pπ - μ + μ - branching fraction is measured relative to the Λ b 0 → J/ ψ(→ μ + μ -) pπ - branching fraction giving B({Λ}_b^0\to p{π}^{-/μ+{μ}-)}{B({Λ}_b^0\to J/ψ (\to {μ}+{μ}-)p{π}-)}=0.044± 0.012± 0.007, where the first uncertainty is statistical and the second is systematic. This is the first observation of a b → d transition in a baryonic decay.16 p.application/pdfengcc-by (c) Camboni, Alessandro et al., 2017https://creativecommons.org/licenses/by/4.0/HadronsGran Col·lisionador d'HadronsFísica de partículesExperimentsHadronsLarge Hadron Collider (France and Switzerland)Particle physicsExperimentsinfo:eu-repo/semantics/article6779852022-06-07info:eu-repo/semantics/openAccess