Type-II Seesaw at Collider, Lepton Asymmetry and Singlet Scalar Dark Matter

TL;DR

This paper introduces a TeV-scale extension of the standard model with a B-L symmetry that explains neutrino masses, dark matter, and leptogenesis, predicting new particles observable at colliders.

Contribution

It presents a novel model where neutrino masses, dark matter stability, and leptogenesis occur independently at the TeV scale, with testable collider signatures.

Findings

Neutrino masses generated via type-II seesaw at TeV scale

Stable singlet scalar dark matter with Planck-suppressed decay

Predicted doubly charged scalar and long-lived fermion at colliders

Abstract

We propose an extension of the standard model with a B-L global symmetry that is broken softly at the TeV scale. The neutrinos acquire masses through a type-II seesaw while the lepton (L) asymmetry arises in the {\it singlet sector} but without B-L violation. The model has the virtue that the scale of L-number violation ($\Lambda$) giving rise to neutrino masses is independent of the scale of leptogenesis ($\Lambda'$). As a result the model can explain {\it neutrino masses, singlet scalar dark matter and leptogenesis at the TeV scale}. The stability of the dark matter is ensured by a surviving $Z_2$ symmetry, which could be lifted at the Planck scale and thereby allowing Planck scale-suppressed decay of singlet scalar dark matter particles of mass $\approx 3$ MeV to $e^+ e^-$ pairs in the Galactic halo. The model also predicts a few hundred GeV doubly charged scalar and a long lived charged fermion, whose decay can be studied at Large Hadron Collider (LHC) and International Linear Collider (ILC).