Search for Invisible Decays of a Dark Photon Produced in e⁺e⁻ Collisions at BaBar

Abstract

We search for single-photon events in 53 fb⁻¹ of e⁺e⁻ collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a large missing momentum and energy, consistent with production of a spin-1 particle A′ through the process e⁺e⁻→γA′; A′→invisible. Such particles, referred to as “dark photons,” are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A′ to e⁺e⁻ in the mass range m[subscript A′] ≤8 GeV. In particular, our limits exclude the values of the A′ coupling suggested by the dark-photon interpretation of the muon (g-2)[subscript μ] anomaly, as well as a broad range of parameters for the dark-sector models.