Speaker
abi Soffer
Description
We report on the latest searches for low mass states predicted in several New Physics models performed with the data collected by the BaBar detector at the PEP-II e+e− collider. In particular, we search for single-photon events in a sample corresponding to 53 fb−1 of e+e− collision data. 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′→e+e− for a dark photon with a mass lower than 8 GeV. In particular, our limits exclude the values of the A′ coupling suggested by the dark-photon interpretation of the muon (g−2) anomaly, as well as a broad range of parameters. We also present a search for a new muonic dark force mediated by a gauge boson (Z′) coupling only to the second and third lepton families. The existence of the Z′ boson is probed in e+e−→μ+μ−Z′, Z′→μ+μ− events, No significant signal is observed. Limits on dark-sector coupling constants are derived, improving the current constraints to the allowed parameter space.
