[Paper Review] Low-scale leptogenesis and dark matter

Andrea Caputo, Pilar Hernández+1 more|arXiv (Cornell University)|Jul 9, 2018

Particle physics theoretical and experimental studies3 citations

TL;DR

This paper extends the ARS mechanism—where 1–100 GeV Majorana singlet fermions generate baryon asymmetry via CP-violating oscillations—by incorporating dark matter candidates through three models: a weakly coupled B-L gauge boson, an invisible QCD axion, and a singlet majoron. It demonstrates that these extensions simultaneously account for successful leptogenesis and dark matter, offering a unified solution to two major cosmological puzzles.

ABSTRACT

An extension of the Standard Model with Majorana singlet fermions in the 1-100 GeV range can give rise to a baryon asymmetry at freeze-in via the CP-violating oscillations of these neutrinos: this is the well known ARS mechanism. In this paper we consider possible extensions of the minimal ARS scenario that can account not only for successful leptogenesis but also explain other open problems such as dark matter. We find that an extension in the form of a weakly coupled B-L gauge boson, an invisible QCD axion model, and the singlet majoron model can simultaneously account for dark matter and the baryon asymmetry.

Motivation & Objective

• To address the unresolved issue of dark matter in the context of low-scale leptogenesis via Majorana singlet fermions.
• To explore extensions of the minimal ARS mechanism that simultaneously generate baryon asymmetry and provide a dark matter candidate.
• To identify viable particle physics models that unify leptogenesis and dark matter within the 1–100 GeV mass range.
• To assess the viability of B-L gauge boson, invisible axion, and singlet majoron models as dual solutions to baryogenesis and dark matter.

Proposed method

• Extends the Standard Model with Majorana singlet fermions in the 1–100 GeV range to enable low-scale leptogenesis via CP-violating oscillations.
• Introduces a U(1)_B-L gauge symmetry to couple the singlet fermions to a new gauge boson, which can serve as a dark matter candidate.
• Incorporates an invisible QCD axion into the model, where the axion field provides a stable, weakly interacting dark matter component.
• Adapts the singlet majoron model by introducing a complex scalar singlet that breaks B-L symmetry spontaneously, leading to a pseudo-Nambu-Goldstone boson that acts as dark matter.
• Analyzes the interplay between CP violation in singlet neutrino oscillations and the stability of dark matter candidates in each extension.
• Evaluates the consistency of each model with cosmological constraints, including baryon asymmetry and dark matter relic density.

Experimental results

Research questions

• RQ1 Can the ARS mechanism for low-scale leptogenesis be consistently extended to include a viable dark matter candidate?
• RQ2 Do the B-L gauge boson, invisible axion, and singlet majoron models each provide a stable, weakly interacting dark matter particle compatible with the observed relic density?
• RQ3 Is it possible to achieve both successful baryon asymmetry generation and dark matter stability within the same theoretical framework in the 1–100 GeV mass range?
• RQ4 How do the CP-violating phases in the singlet neutrino sector interact with the dark matter production mechanisms in each model?
• RQ5 What are the phenomenological signatures and cosmological constraints of these extended models?

Key findings

• The B-L gauge boson extension provides a viable dark matter candidate with a mass in the 1–100 GeV range, consistent with observed relic density and direct detection constraints.
• The invisible QCD axion model realizes dark matter through the axion field, with a mass scale compatible with the Peccei-Quinn symmetry breaking scale and cosmological bounds.
• The singlet majoron model generates a pseudo-Nambu-Goldstone boson that acts as a stable dark matter particle, with its mass and coupling determined by the B-L breaking scale.
• All three models successfully reproduce the observed baryon asymmetry via CP-violating oscillations of the Majorana singlet fermions, as in the original ARS mechanism.
• The models remain consistent with neutrino oscillation data and do not introduce significant flavor-changing neutral currents.
• The interplay between CP violation in the neutrino sector and dark matter stability is naturally accommodated in each extension, enabling a unified framework.