Search for slowly moving magnetic monopoles with the MACRO detector

A search for slowly moving magnetic monopoles in the cosmic radiation was conducted from October 1989 to November 1991 using the large liquid scintillator detector subsystem of the first supermodule of the MACRO detector at the Gran Sasso underground laboratory. The absence of candidates established an upper limit on the monopole flux of 5.6×${10}^{\mathrm{-}15}$ ${\mathrm{cm}}^{\mathrm{-}2}$ ${\mathrm{sr}}^{\mathrm{-}1}$ ${\mathrm{s}}^{\mathrm{-}1}$ at 90% confidence level in the velocity range of ${10}^{\mathrm{-}4}$≲β<4×${10}^{\mathrm{-}3}$. This result places a new constraint on the abundance of monopoles trapped in our solar system.