Garcia Moreno, PaulaGarrido Beltrán, LluísGironella Gironell, PereGomez Fernandez, SergioGraugés Pous, EugeniLobo Salvia, AniolLópez Huertas, AlbertManera Escalero, RafelMarin Benito, CarlaMauricio Ferre, JoanAlfonso Albero, AlejandroVazquez Gomez, RicardoLHCb Collaboration2025-07-042025-07-0420231126-6708https://hdl.handle.net/2445/222021Abstract: The B+ → Jψη0K+ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb−1 . The branching fraction of this decay is measured relative to the known branching fraction of the B+ → ψ(2S)K+ decay and found to be B(B+ → Jψη0K+) B(B+ → ψ(2S)K+) = (4.91 ± 0.47 ± 0.29 ± 0.07) × 10−2 , where the first uncertainty is statistical, the second is systematic and the third is related to external branching fractions. A first look at the J/ψη0 mass distribution is performed and no signal of intermediate resonances is observed.27 p.application/pdfengcc-by (c) Aaij, R. et al., 2023http://creativecommons.org/licenses/by/4.0/Física de partículesHadronsParticle physicsHadronsinfo:eu-repo/semantics/article7565812025-07-04info:eu-repo/semantics/openAccess