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 Z(2) 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. (C) 2011 Elsevier B.V. All rights reserved.