Inclusive Dark Photon Search at LHCb

Abstract

We propose an inclusive search for dark photons $A^{\prime }$ at the LHCb experiment based on both prompt and displaced di-muon resonances. Because the couplings of the dark photon are inherited from the photon via kinetic mixing, the dark photon $A^{\prime }\to {\mu }^{+}{\mu }^{-}$ rate can be directly inferred from the off-shell photon ${\gamma }^{\ast }\to {\mu }^{+}{\mu }^{-}$ 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.

Comments: 5+5 pages, 5 figures; v2: approximate version to appear in PRL, enlarged figure at end