Radiation zeros and a test for thegvalue of theτlepton

We suggest that an experimental test for the $g$ value of the $\tau$ lepton may be feasible. The idea is to take advantage of the radiation zero which occurs in the radiative decays $\tau \to e\nu \overline{\nu }\gamma$ and $\tau \to \mu \nu \overline{\nu }\gamma$ for $g=2\mathrm{}$. We calculate the differential decay rate for an arbitrary $g$ value of the $\tau$. The results for back-to-back electron- (muon-) photon events with large electron (muon) energies are indeed sensitive to the $g$ value of the $\tau$. Our estimates for the expected event rates are not unreasonable and one could hope to achieve a reasonable upper bound for $g$, perhaps even a measured value.