# Type III Seesaw for Neutrino Masses in $U(1)_{B-L}$ Model with Multi-component Dark Matter

## TL;DR

This paper introduces a $B-L$ extended Standard Model with type III seesaw mechanism, featuring two stable dark matter components from fractional charges, and discusses phenomenological constraints and collider prospects.

## Contribution

It presents a novel anomaly-free $B-L$ model with fermion triplets and fractional charges, naturally producing multi-component dark matter without extra symmetries.

## Key findings

- Model is consistent with phenomenological constraints.
- Dark matter candidates are stable due to residual symmetries.
- Enhanced collider signatures due to additional gauge bosons.

## Abstract

We propose a $B-L$ gauged extension of the Standard Model where light neutrino masses arise from type III seesaw mechanism. Unlike the minimal $B-L$ model with three right handed neutrinos having unit lepton number each, the model with three fermion triplets is however not anomaly free. We show that the leftover triangle anomalies can be cancelled by two neutral Dirac fermions having fractional $B-L$ charges, both of which are naturally stable by virtue of a remnant $\mathbb{Z}_2 \times \mathbb{Z}'_2$ symmetry, naturally leading to a two component dark matter scenario without any ad-hoc symmetries. We constrain the model from all relevant phenomenological constraints including dark matter properties. Light neutrino mass and collider prospects are also discussed briefly. Due to additional neutral gauge bosons, the fermion triplets in type III seesaw can have enhanced production cross section in collider experiment.