Search for Tachyon Monopoles

We have searched for a magnetically charged particle that travels faster than light. These particles are detected by the Cherenkov radiation they emit while moving in a magnetic field. We find that the cross sections for photoproduction of these particles by 1-MeV $\gamma$ rays in lead and water are less than 0.6 × ${10}^{-36\mathrm{}}$ ${\mathrm{cm}}^2$ and 2 × ${10}^{-36\mathrm{}}$ ${\mathrm{cm}}^2$, respectively. These results are subject to some assumptions about the hypothetical particles.