Dark-Portal Leptogenesis in a Non-Holomorphic Modular Scoto-Seesaw Model

TL;DR

This paper presents a non-holomorphic modular scoto-seesaw model that explains neutrino masses and successful low-scale leptogenesis via CP violation from a complex modulus, predicting observable collider signatures.

Contribution

It introduces a novel non-holomorphic $A_4$ modular framework for neutrino phenomenology and leptogenesis, avoiding resonant conditions and linking dark sector physics to collider signals.

Findings

Viable parameter space for the modulus $ au$ consistent with neutrino oscillation data.

Successful low-scale leptogenesis driven by CP violation from the complex modulus.

Potential collider signature of long-lived charged particles $ au^{ ext{±}}$.

Abstract

This work explores the neutrino phenomenology of the scotoseesaw model under non-holomorphic $A_4$ modular flavor symmetry providing a non-SUSY framework for realization of the modular symmetry. To prevent mixing between the beyond standard model fields associated with the tree and loop-level neutrino mass contributions, we assign even and odd modular weights to these sectors, respectively. The physical allowed ranges of oscillation parameters are used to identify the viable region of modulus parameter $\tau$ in its fundamental domain. With the complex modulus $\tau$ serving as the unique source of CP violation (all other parameters are real) the framework realizes successful low-scale leptogenesis through CP-violating decays of the lightest right-handed neutrino into Standard Model leptons and the Higgs boson. The requisite CP asymmetry arises from one-loop diagrams involving dark-sector states, obviating the need for degenerate mass spectra and thereby circumventing the usual resonant leptogenesis mechanism. The observation of a long-lived charged particle ($\eta^{\pm}$) in collider experiments would offer compelling evidence for the inert scalar sector of the model and provide a crucial experimental hint on the dark-sector assisted generation of neutrino masses and leptogenesis.