Event Details

Short baseline neutrino experiments such as LSND and MiniBooNE seem to suggest the existence of light sterile neutrinos. However, this is in tension with the cosmological bounds on the effective number of neutrinos N_{eff}. Dr. Chiu Man Ho will demonstrate that if an MeV dark matter couples more strongly to electrons and/or photons than to neutrinos, then p-wave annihilation after neutrino decoupling can significantly reduce N_{eff} inferred from PLANCK. The dark matter annihilation also weakens the cosmological upper bounds on the neutrino masses. Coincidentally, a dark matter particle with these properties and lighter than 3 MeV is precisely one that can explain the 511 keV gamma-ray line observed by INTEGRAL. Dr. Ho will then show that the addition of sterile neutrinos allows this kind of dark matter to be lighter than 3 MeV, which is otherwise ruled out by the bound on N_{eff} if only active neutrinos are considered. Finally, Dr. Ho will discuss possible dark matter models for this purpose.

Video Recording