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-→γ A' ; 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 mA'≤8 GeV . In particular, our limits exclude the values of the A' coupling suggested by the dark-photon interpretation of the muon (g -2 )μ anomaly, as well as a broad range of parameters for the dark-sector models.