Dark-portal leptogenesis in a nonholomorphic modular scoto-seesaw model

This work explores the neutrino phenomenology of the scoto-seesaw model under nonholomorphic A 4 modular flavor symmetry providing a nonsupersymmetry 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 τ in its fundamental domain. With the complex modulus τ serving as the unique source of C P violation (all other parameters are real), the framework realizes successful low-scale leptogenesis through C P -violating decays of the lightest righthanded neutrino into Standark model leptons and the Higgs boson. The requisite C P 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 ( η ± ) in collider experiments would offer compelling evidence for the inert scalar sector of the model and provide a crucial experimental hint as to the dark-sector-assisted generation of neutrino masses and leptogenesis.