Exploring Neutrinoless Double Beta Decay in The 3+3 Model

Abstract

Sterile neutrinos, non-interacting fermion singlets, are crucial in BSM physics, addressing oscillation anomalies and facilitating neutrino mass generation via type-I seesaw mechanism. We investigate a model extending the SM with 3 sterile neutrino states, employing a specific (6 × 6) unitary mixing matrix. Analytically deriving the masses of added sterile states using the exact seesaw relation, we study their impact on |mee|, relevant to neutrinoless double beta decay (0νββ) searches. Exploring the parameter space of |mee| with consideration of 0νββ sensitivity, we incorporate constraints from charged lepton flavor violation (cLFV) and non-unitarity effects, including additional CP-violating phases and active-sterile mixing angles. Our analysis also assesses the branching ratio of µ → eγ, a key cLFV process, within this framework.