  The positron anomaly recently reported by the cosmic-ray measurements
suggests that, if explained by the decay of dark matter particle, the decay
source is closely linked up with the leptonic sector of the standard model. It
is observed that, with a simple dimensional analysis, the lifetime of dark
matter for the anomaly is expressed by the energy scale of neutrino masses. We
present two scenarios in which these two matter at issue (the dark matter width
and the tiny neutrino masses) stem from a single operator involving a
gauge-singlet scalar field.
