TeV Scale Modified Type-II Seesaw and Dark Matter in a Gauged $U(1)_{\rm B-L}$ Symmetric Model

Abstract

In an endeavor to explain the light neutrino masses and dark matter (DM) simultaneously, we study a gauged $U(1)_{\rm B-L}$ extension of the standard model (SM). The neutrino masses are generated through a variant of type-II seesaw mechanism in which one of the scalar triplets has a mass in a scale that is accessible at the present generation colliders. Three SM singlet right chiral fermions $\chi_{iR}$($i=e,\mu,\tau$) with $\rm B-L$ charges -4, -4, +5 are invoked to cancel the $\rm B-L$ gauge anomalies and the lightest one among these three fermions becomes a viable DM candidate as their stability is guaranteed by a remnant $\mathcal Z_2$ symmetry to which $U(1)_{\rm B-L}$ gauge symmetry gets spontaneously broken. Interestingly in this scenario, the neutrino mass and the co-annihilation of DM are interlinked through the breaking of $U(1)_{\rm B-L}$ symmetry. Apart from giving rise to the observed neutrino mass and dark matter abundance, the model also predicts exciting signals at the colliders. Especially we see a significant enhancement in the production cross-section of the TeV scale doubly charged scalar in presence of the $Z_{\rm BL}$ gauge boson. We discuss all the relevant constraints on model parameters from observed DM abundance and null detection of DM at direct and indirect search experiments as well as the constraints on the $\rm B-L$ gauge boson from recent colliders.