Search for Slow Magnetic Monopoles with the NOvA Detector on the Surface

We report a search for a magnetic monopole component of the cosmic-ray flux in a 95-day exposure of the NOvA experiments Far Detector, a 14 kt segmented liquid scintillator detector designed primarily to observe GeV-scale electron neutrinos. No events consistent with monopoles were observed, setting an upper limit on the flux of $2times 10^{-14} mathrm{cm^{-2}s^{-1}sr^{-1}}$ at 90% C.L. for monopole speed $6times 10^{-4} < beta < 5times 10^{-3}$ and mass greater than $5times 10^{8}$ GeV. Because of NOvAs small overburden of 3 meters-water equivalent, this constraint covers a previously unexplored low-mass region.