Singlet scalar dark matter in U(1) < inf > B-L < /inf > models without right-handed neutrinos

Abstract

We investigate the phenomenology of singlet scalar dark matter in a simple B-L gauge extension of the Standard Model where the dark matter particle is charged under the U(1)B-L symmetry. The non-trivial gauge anomalies are cancelled with the introduction of three exotic fermions with B-L charges as −4, −4, 5, instead of right-handed neutrinos νRi (i = 1, 2, 3), with B-L = −1 in the conventional U(1)B-L model. Without the need of any ad hoc discrete symmetry, the B-L charge plays a crucial role in stabilizing the dark matter. We make a comprehensive study of dark matter phenomenology in the scalar and gauge portals separately. In the gauge-mediated regime, we invoke the LEP-II constraints and dilepton limits of ATLAS on the gauge parameters. A massless physical Goldstone plays a vital role in the scalar-portal dark matter observables, becomes a unique feature of the model. We show the mechanism of generating the light neutrino mass at one-loop level, where the dark matter singlet runs in the loop. We shed light on the semi-annihilation and, finally, we comment on indirect signals in this framework.