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

## TL;DR

This study searches for invisible decays of dark photons in electron-positron collisions using BaBar data, setting upper limits on their coupling strength and excluding certain dark-sector model parameters.

## Contribution

First search for invisible dark photon decays in e+e- collisions at BaBar, providing new constraints on dark photon properties and dark matter models.

## Key findings

- No evidence for dark photon production was observed.
- Set 90% confidence level upper limits on the coupling strength of dark photons.
- Excluded dark photon parameters suggested by the muon g-2 anomaly.

## 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->gamma 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 m_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) anomaly, as well as a broad range of parameters for the dark-sector models.