Abellan Beteta, CarlosCalvo Gómez, MíriamCamboni, AlessandroComerma Montells, AlbertDomingo Bonal, FrancescGarrido Beltrán, LluísGascón Fora, DavidGrabalosa Gándara, MarcGraciani Díaz, RicardoGraugés Pous, EugeniLópez Asamar, EliasMusy, MarcoPérez-Calero Yzquierdo, AntonioPicatoste Olloqui, EduardoPie Valls, B. (Blai)Potterat, CédricPuig Navarro, AlbertRoselló, M.Ruiz, Hugo (Ruiz Pérez)Vázquez Gómez, RicardVilasis-Cardona, XavierLHCb Collaboration2019-05-222019-05-222012-06-110031-9007https://hdl.handle.net/2445/133690The interference between the K + K − S -wave and P -wave amplitudes in B 0 s → J / ψ K + K − decays with the K + K − pairs in the region around the ϕ ( 1020 ) resonance is used to determine the variation of the difference of the strong phase between these amplitudes as a function of K + K − invariant mass. Combined with the results from our C P asymmetry measurement in B 0 s → J / ψ ϕ decays, we conclude that the B 0 s mass eigenstate that is almost C P = + 1 is lighter and decays faster than the mass eigenstate that is almost C P = − 1 . This determines the sign of the decay width difference Δ Γ s ≡ Γ L − Γ H to be positive. Our result also resolves the ambiguity in the past measurements of the C P violating phase ϕ s to be close to zero rather than π . These conclusions are in agreement with the standard model expectations.7 p.application/pdfengcc by (c) CERN; LHCb Collaboration, 2012http://creativecommons.org/licenses/by/3.0/es/Física de partículesExperimentsParticle physicsExperimentsinfo:eu-repo/semantics/article6189782019-05-22info:eu-repo/semantics/openAccess