Enhanced tau neutrino appearance through invisible decay

The decay of neutrino mass eigenstates leads to a change of the conversion and survival probability of neutrino flavor eigenstates. Exploiting the recent results released by the long-baseline OPERA experiment we perform the statistical investigation of the neutrino invisible decay hypothesis in the ν μ → ν τ appearance channel. We find that the neutrino decay provides an enhancement of the expected tau appearance signal with respect to the standard oscillation scenario for the long-baseline OPERA experiment. The increase of the ν μ → ν τ conversion probability by the decay of one of the mass eigenstates is due to a reduction of the “destructive interference” among the different massive neutrino components. Despite data showing a very mild preference for invisible decays with respect to the oscillations only hypothesis, we provide an upper limit for the neutrino decay lifetime in this channel of τ 3 / m 3 ≳ 1.3 × 10 − 13     s / eV at the 90% confidence level.