Renormalization Group Study of the Minimal Majoronic Dark Radiation and Dark Matter Model

TL;DR

This paper investigates the renormalization group evolution of a minimal Majoron model that explains dark radiation and dark matter, predicting specific particle masses, mixing angles, and potential signals in neutrino detectors.

Contribution

It provides a comprehensive numerical analysis of the model's parameter space, identifying viable dark matter and neutrino mass scenarios, and explores potential experimental signatures.

Findings

Heavy scalar dark matter mass 1.5-4 TeV for stability

Predicted scalar S mass 10-100 GeV with large Higgs mixing

Potential signals in rare Z decays and neutrino detectors

Abstract

We study the 1-loop renormalization group equation running in the simplest singlet Majoron model constructed by us earlier to accommodate the dark radiation and dark matter content in the universe. A comprehensive numerical study was performed to explore the whole model parameter space. A smaller effective number of neutrinos $\triangle N_{eff}\sim 0.05$, or a Majoron decoupling temperature higher than the charm quark mass, is preferred. We found that a heavy scalar dark matter, $\rho$, of mass $1.5-4$ TeV is required by the stability of the scalar potential and an operational type-I see-saw mechanism for neutrino masses. A neutral scalar, $S$, of mass in the $10-100$ GeV range and its mixing with the standard model Higgs as large as $0.1$ is also predicted. The dominant decay modes are $S$ into $b\bar{b}$ and/or $\omega\omega$. A sensitive search will come from rare $Z$ decays via the chain $Z\rightarrow S+ f\bar{f}$, where $f$ is a Standard Model fermion, followed by $S$ into a pair of Majoron and/or b-quarks. The interesting consequences of dark matter bound state due to the sizable $S\rho \rho$-coupling are discussed as well. In particular, shower-like events with an apparent neutrino energy at $M_\rho$ could contribute to the observed effective neutrino flux in underground neutrino detectors such as IceCube.