New experimental limit on the stability of the electron

A lower limit of 1.5×${10}^{25}$ yr (68% C.L.) is reported for the mean life of the electron decay via the branch $e^{\mathrm{-}}$→γ+${\nu }_e$. This is significantly longer than the best previously reported limit. Data were collected for 8850 h with an ultralow-background 135-${\mathrm{cm}}^3$ Ge detector located 1438 m underground. The electrons of primary interest are in the germanium crystal and in 102 kg of copper surrounding the detector. A projection of the ultimate limit on the half-life for this decay mode which would be attainable using this technique, under the most optimistic circumstances, is about 3 orders of magnitude higher.