  Supernova neutrinos could be well-suited for probing neutrino decay, since
decay may be observed even for very small decay rates or coupling constants. We
will introduce an effective operator framework for the combined description of
neutrino decay and neutrino oscillations for supernova neutrinos, which can
especially take into account two properties: One is the radially symmetric
neutrino flux, allowing a decay product to be re-directed towards the observer
even if the parent neutrino had a different original direction of propagation.
The other is decoherence because of the long baselines for coherently produced
neutrinos. We will demonstrate how to use this effective theory to calculate
the time-dependent fluxes at the detector. In addition, we will show the
implications of a Majoron-like decay model. As a result, we will demonstrate
that for certain parameter values one may observe some effects which could also
mimic signals similar to the ones expected from supernova models, making it in
general harder to separate neutrino and supernova properties.
