Title: CMB Non-Gaussianity from Recombination and Hints for Dark Matter off the Beaten Track"


We show that dark matter annihilation around the time of recombination can lead to growing ionization modes that track the collapse of dark matter overdensities. This amplifies small scale cosmological perturbations to the free electron density by a significant amount. Electron perturbations lead to CMB non-gaussianity, offering a means of detection by Planck and other experiments. We present a novel analytic calculation of CMB non-gaussianity from recombination, improving over previous analyses by taking proper care of small scale electron perturbations and providing a clear identification of the relevant physical processes. We show that, even though electron perturbations can be markedly boosted compared with the standard model prediction, the effect of dark matter annihilation in the CMB bispectrum will be difficult to detect.