Unique search for grand unification magnetic monopoles

Abstract

We describe a new technique for searching for slowly moving, supermassive magnetic monopoles employing a single thick slab of PS-10 acrylic scintillator at sea level. Monopoles would be identified by the abnormally wide photomultiplier-tube anode signal produced as they traverse the thick slab at very low velocity ($\sim {10}^{-3\mathrm{}} c$). The scintillation response to supermassive monopoles is reviewed, and the results of a calculation of the response of PS-10 are presented. No monopole candidates were observed in 3852 h of running time, and a limit on the flux $F$ of supermassive monopoles, $F\lesssim 4.1\times {10}^{-13\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ ${\mathrm{s}}^{-1\mathrm{}}$ (single-event significance) for monopole velocities $6\times {10}^{-4\mathrm{}} c\lesssim V<\mathrm{}2.1\mathrm{}\times {10}^{-3\mathrm{}} c$, is set. This result is compared to other experimental limits and to theoretical limits on the flux.