How to interpret a discovery or null result of the 0ν2β decay

The Majorana nature of massive neutrinos will be crucially probed in the next-generation experiments of the neutrinoless double-beta ( 0ν2β ) decay. The effective mass term of this process, ⟨m⟩ee , may be contaminated by new physics. So how to interpret a discovery or null result of the 0ν2β decay in the foreseeable future is highly nontrivial. In this paper we introduce a novel three-dimensional description of |⟨m⟩ee| , which allows us to see its sensitivity to the lightest neutrino mass and two Majorana phases in a transparent way. We take a look at to what extent the free parameters of |⟨m⟩ee| can be well constrained provided a signal of the 0ν2β decay is observed someday. To fully explore lepton number violation, all the six effective Majorana mass terms ⟨m⟩αβ (for α,β=e,μ,τ ) are calculated and their lower bounds are illustrated with the two-dimensional contour figures. The effect of possible new physics on the 0ν2β decay is also discussed in a model-independent way. We find that the result of |⟨m⟩ee| in the normal (or inverted) neutrino mass ordering case modified by the new physics effect may somewhat mimic that in the inverted (or normal) mass ordering case in the standard three-flavor scheme. Hence a proper interpretation of a discovery or null result of the 0ν2β decay may demand extra information from some other measurements

Geometry of the effective Majorana neutrino mass in the 0??? decay

The neutrinoless double-beta (0???) decay is a unique process used to identify the Majorana nature of massive neutrinos, and its rate depends on the size of the effective Majorana neutrino mass ?m?ee. We put forward a novel ?coupling-rod? diagram to describe ?m?ee in the complex plane, by which the effects of the neutrino mass ordering and CP-violating phases on ?m?ee are intuitively understood. We show that this geometric language allows us to easily obtain the maximum and minimum of |?m?ee|. It remains usable even if there is a kind of new physics contributing to ?m?ee, and it can also be extended to describe the effective Majorana masses ?m?e?, ?m?e?, ?m???, ?m??? and ?m??? which may appear in some other lepton-number violating processes

Lepton mixing parameters from Δ(48) family symmetry and generalised CP

We provide a systematic and thorough exploration of the Δ(48) family symmetry and the consistent generalised CP symmetry. A model-independent analysis of the achievable lepton flavor mixing is performed by considering all the possible remnant symmetries in the neutrino and the charged lepton sectors. We find a new interesting mixing pattern in which both lepton mixing angles and CP phases are nontrivial functions of a single parameter θ . The value of θ can be fixed by the measured reactor mixing angle θ 13 , and the excellent agreement with the present data can be achieved. A supersymmetric model based on Δ(48) family symmetry and generalised CP symmetry is constructed, and this new mixing pattern is exactly reproduced