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A lower limit of > 1.22 x 10²⁶years (68% c.l.) has been determined
for the mean life time of electron decay via the branch e^- ---> gamma + nu_e.
The limit was deduced from the spectra measured in the period 1995-2003
with the full set-up of 5 enriched ⁷⁶Ge detectors
of the HEIDELBERG-MOSCOW beta-beta experiment in the Gran-Sasso underground laboratory.
One of the detectors, and the setup 1 consisting of four detectors show an indication
of a signal on a 1.4 sigma C.L.
The best limit given by a single detector is 1.93 x 10²⁶ y.
The result is the by far sharpest limit obtained with Ge detectors.
When comparing it with other limits, e.g. that from BOREXINO \cite{Borex02}
it may be essential to note that the present limit has been deduced
from the raw data without any treatment of the background.
Combined with the best laboratory limit on the photon mass
it gives the following restriction for charge nonconservation:
epsilon__{e nu gamma} < 0.86 x 10^-98 (68% c.l.) or < 1.14 x 10^-97 (90% c.l.).
-------- Abstract --------