Singlet scalar dark matter in U(1)_B-L 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 $\nu_{Ri} (i=1,2,3)$, 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.