The transverse polarization of electrons emitted in the $\beta$ decay of polarized ${}^8\mathrm{L}\mathrm{i}$ nuclei has been measured. For the time-reversal violating triple correlation parameter we find $R=(0.9\pm 2.2)\times {10}^{-3}$. This result is in agreement with the standard model and yields improved constraints on exotic tensor contributions to the weak interaction. Combined with other experimental results and using a model for the coupling constants, a new limit for the mass of a possible scalar leptoquark, $m_{\mathrm{L}\mathrm{Q}}>560\mathrm{G}\mathrm{e}\mathrm{V}/c^2$ (90% C.L.), is obtained.

• Received 6 January 2003

DOI:https://doi.org/10.1103/PhysRevLett.90.202301