  A new experiment studying the behavior of a radioactive ion before its weak
decay by K-capture suggests that neutrino masses and mixing can be investigated
without detecting the neutrino. Every weak decay can be observed, thus avoiding
the suppression by the low neutrino absorption cross section of the signal in
conventional neutrino oscillation experiments. The normally unobservable long
wave lengths are made observable by having the radioactive source move a long
distance circulating around in a storage ring. A new oscillation phenomenon
with nonexponential decay arises in this "watched pot" experiment where
continous monitoring sets the decay clock back to zero while preserving
oscillating phases in the initial state. The initial ion wave packet has a
momentum spread required by Heisenberg and contains pairs of components with
different momenta and energies. These can produce neutrino amplitudes in two
mass eigenstates with different momenta which mix to produce a single $\nu_e$
state. In this typical quantum mechanics "two-slit" or "which path" experiment
a transition between the same initial and final states can go via two paths in
energy-momentum space. Their relative phases change with the propagation of the
initial state between the points of entry and decay. The oscillations produced
by these phase changes are shown to be consistent with quantum mechanics and
causality.
