Upper Limit on Flux of Cosmic-Ray Monopoles Obtained with a Three-Loop Superconductive Detector

A three-loop superconductive monopole detector has been continuously operated for over 150 days. Its sensing area is 476 ${\mathrm{cm}}^2$ (71 ${\mathrm{cm}}^2$ loop area and 405 ${\mathrm{cm}}^2$ near-miss area) for double coincidence events. The data, which contain no candidate events, set an upper limit of 3.7 × ${10}^{-11\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ (90% C.L.) for monopoles of any mass and at any velocity passing through the Earth's surface.