A recent measurement of the ${\pi }^{-}\to e{\overline{\nu }}_e\gamma$ branching ratio is in disagreement with vector-axial-vector interactions assumed in the standard model. Poblaguev has proposed that a tensor current can effectively account for this discrepancy, arguing that the strength required is not in disagreement with constraints obtained from nuclear $\beta$ decay and $\mu$ decay. We point out here that the nuclear $\beta$-decay constraint may be much tighter than Poblaguev calculates, possibly leading to serious disagreement between the nuclear $\beta$-decay limits and the proposed tensor contribution in ${\pi }^{-}\to e{\overline{\nu }}_e\gamma$.

• Received 24 August 1992

DOI:https://doi.org/10.1103/PhysRevD.47.1247