Semi-annihilating dark matter coupled with Majorons

TL;DR

This paper proposes a semi-annihilating dark matter model involving Majorons that can form halo cores and produce detectable neutrino signatures, offering an alternative to traditional weakly interacting massive particles.

Contribution

It introduces a novel semi-annihilating dark matter model with Majorons, demonstrating its effects on halo structure and potential neutrino signals.

Findings

Semi-annihilation induces dark matter halo core formation.

Model predicts a distinctive neutrino spectrum from Majoron decay.

Parameter space allows detection prospects at Hyper-Kamiokande.

Abstract

The thermal production mechanism of dark matter is attractive and well-motivated by predictivity. A representative of this type of dark matter candidate is the canonical, weakly interacting massive particles. An alternative is semi-annihilating dark matter, which exhibits different phenomenological aspects from the former example. In this study, we constructed a model of dark matter semi-annihilating into a pair of anti-dark matter and a Majoron based on a global $U(1)_{B-L}$ symmetry, and show that semi-annihilation induces the core formation of dark matter halos, which can alleviate the so-called small-scale problems. In addition, the box-shaped spectrum of neutrinos was produced by the subsequent decay of the Majoron. This can be a distinctive signature of the dark matter in the model. We find a parameter space where the produced neutrinos can be detected by the future large-volume neutrino detector Hyper-Kamiokande. We also compared the dark matter scenario with the case of halo core formation by the strongly self-interacting dark matter.