Proposed Inclusive Dark Photon Search at LHCb

We propose an inclusive search for dark photons A^' at the LHCb experiment based on both prompt and displaced dimuon resonances. Because the couplings of the dark photon are inherited from the photon via kinetic mixing, the dark photon A^'→μ⁺μ^- rate can be directly inferred from the off-shell photon γ*→μ⁺μ^- rate, making this a fully data-driven search. For run 3 of the LHC, we estimate that LHCb will have sensitivity to large regions of the unexplored dark-photon parameter space, especially in the 210--520 MeV and 10--40 GeV mass ranges. This search leverages the excellent invariant-mass and vertex resolution of LHCb, along with its unique particle-identification and real-time data-analysis capabilities.