Improved experimental limits on the production of magnetic monopoles

The existence of magnetic monopoles of charge g explains the quantization of electric charge e as e g = nℏc/2, n = ±1, ±2,..., results in the dual symmetrization of Maxwell's equations, and is not forbidden by any known principles of physics. The minimum values of the quantization number are n = 1 according to Dirac and n = 2 according to Schwinger. For e being the charge on the electron, these values are n = 3 and n = 6, respectively, if quantization with the quark electric charges is allowed. Previous searches for trapped and bound magnetic monopoles in samples from various accelerators, in meteorites, and lunar soil have been made. Since the Tevatron proton-antiproton (p p̄) collider has extended its integrated luminosity by a factor of some 10 000 over the last search of Bertani et al. (1990) the authors have taken samples exposed in the D0 experiment and performed a search that improves these limits. They authors use the induction method of Alvarez et al. (1963) to measure the magnetic charge content of macroscopic Al and Be samples.