Dark Matter and neutrino masses from global U(1)B−L symmetry breaking

We present a scenario where neutrino masses and Dark Matter are related due to a global U(1)B−L symmetry. Specifically we consider neutrino mass generation via the Zee-Babu two-loop mechanism, augmented by a scalar singlet whose VEV breaks the global U(1)B−L symmetry. In order to obtain a Dark Matter candidate we introduce two Standard Model singlet fermions. They form a Dirac particle and are stable because of a remnant Z2 symmetry. Hence, in this model the stability of Dark Matter follows from the global U(1)B−L symmetry. We discuss the Dark Matter phenomenology of the model, and compare it to similar models based on gauged U(1)B−L. We argue that in contrast to the gauged versions, the model based on the global symmetry does not suffer from severe constraints from Z′ searches.