Dark-portal leptogenesis in non-holomorphic modular scoto-seesaw model

The authors present a scoto-seesaw framework based on non-holomorphic A4 modular flavour symmetry, providing a non-supersymmetric realisation of modular symmetry. The model separates tree and loop-level neutrino mass sectors through modular weights and identifies the viable complex modulus τ from neutrino oscillation data. With τ as the sole source of CP violation, successful low-scale leptogenesis is realised through right-handed neutrino decays, with the CP asymmetry generated by dark-sector loop effects without requiring resonant enhancement. The authors discuss the distinctive collider signature of a long-lived charged scalar η, linking the inert sector to neutrino mass generation and leptogenesis.