New Physics in ΔL = 2 neutrino oscillations

We propose a general framework to constrain ΔL = 2 processes by measuring observables associated with neutrino-antineutrino oscillations in π± decays. First, we use this formalism as a new strategy for detecting the CP-violating phases and the effective mass of muon Majorana neutrinos. Within the generic framework of quantum field theory, we compute the non-factorizable probability for producing a pair of same-charged muons in π± decays as a distinctive signature of νμ-ν*μ. Using the neutrino-antineutrino oscillation probability reported by MINOS collaboration, a new stringent bound on the effective muon-neutrino mass is derived. Secondly, we interpret the production of the pair of same-charged muons as a result of lepton number violating (LNV) interactions at the neutrino source, which allow us to constrain New Physics.