LHCb CollaborationAdeva Andany, BernardoÁlvarez Cartelle, PaulaDosil Suárez, ÁlvaroFernández Albor, Víctor ManuelGallas Torreira, Abraham AntonioHernando Morata, José ÁngelPazos Álvarez, AntonioPérez Trigo, EliseoPlo Casasus, MáximoRomero Vidal, AntonioSaborido Silva, Juan JoséSanmartín Sedes, BraisSantamarina Ríos, CibránSeco Miguélez, Marcos AntonioVázquez Regueiro, PabloVázquez Sierra, CarlosVieites Díaz, María2020-04-282020-04-282014Aaij, R., Adeva, B., Adinolfi, M. et al. Observation of the Λ0b → J/ψ pπ − decay. J. High Energ. Phys. 2014, 103 (2014). https://doi.org/10.1007/JHEP07(2014)1031029-8479http://hdl.handle.net/10347/21838The first observation of the Cabibbo-suppressed decay Λ 0b → J/ψpπ − is reported using a data sample of proton-proton collisions at 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. A prominent signal is observed and the branching fraction relative to the decay mode Λ 0b → J/ψpK − is determined to be B(Λ0b→J/ψpπ−)B(Λ0b→J/ψpK−)=0.0824±0.0025 (stat)±0.0042 (syst). A search for direct CP violation is performed. The difference in the CP asymmetries between these two decays is found to be ACP(Λ0b→J/ψpπ−)−ACP(Λ0b→J/ψpK−)=(+5.7±2.4 (stat)±1.2 (syst))%, which is compatible with CP symmetry at the 2.2σ level.eng© CERN, for the benefit of the LHCb Collaboration. Article funded by SCOAP3.This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0), which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were madehttps://creativecommons.org/licenses/by/4.0B physicsCP violationBranching fractionFlavor physicsHadron-Hadron Scatteringjournal article10.1007/JHEP07(2014)103open access