Alfonso Albero, AlejandroCalvo Gómez, MíriamCamboni, AlessandroCoquereau, SamuelGarrido Beltrán, LluísGascón Fora, DavidGraciani Díaz, RicardoGraugés Pous, EugeniLHCb CollaborationMarin Benito, Carla2019-04-262019-04-262018-02-080031-9007https://hdl.handle.net/2445/132476Searches are performed for both promptlike and long-lived dark photons, A ′ , produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using A ′ → μ + μ − decays and a data sample corresponding to an integrated luminosity of 1.6     fb − 1 collected with the LHCb detector. The promptlike A ′ search covers the mass range from near the dimuon threshold up to 70 GeV, while the long-lived A ′ search is restricted to the low-mass region 214 < m ( A ′ ) < 350     MeV . No evidence for a signal is found, and 90% confidence level exclusion limits are placed on the γ - A ′ kinetic-mixing strength. The constraints placed on promptlike dark photons are the most stringent to date for the mass range 10.6 < m ( A ′ ) < 70     GeV , and are comparable to the best existing limits for m ( A ′ ) < 0.5     GeV . The search for long-lived dark photons is the first to achieve sensitivity using a displaced-vertex signature.11 p.application/pdfengcc by (c) CERN; LHCb Collaboration, 2018http://creativecommons.org/licenses/by/3.0/es/Física de partículesExperimentsParticle physicsExperimentsinfo:eu-repo/semantics/article6847202019-04-26info:eu-repo/semantics/openAccess