Constraining Dark Matter-Neutrino Interactions using the CMB and Large-Scale Structure

International audienceWe present a new study on the elastic scattering cross section of dark matter(DM) and neutrinos using the latest cosmological data from Planck andlarge-scale structure experiments. We find that the strongest constraints areset by the Lyman-alpha forest, giving sigma_{DM-neutrino} < 10^{-33} (m_DM/GeV)cm^2 if the cross section is constant and a present-day value ofsigma_{DM-neutrino} < 10^{-45} (m_DM/GeV) cm^2 if it scales as the temperaturesquared. These are the most robust limits on DM-neutrino interactions to date,demonstrating that one can use the distribution of matter in the Universe toprobe dark ("invisible") interactions. Additionally, we show that scenariosinvolving thermal MeV DM and a constant elastic scattering cross sectionnaturally predict (i) a cut-off in the matter power spectrum at the Lyman-alphascale, (ii) N_eff ~ 3.5 +/- 0.4, (iii) H_0 ~ 71 +/- 3 km/s/Mpc and (iv) thepossible generation of neutrino masses