Relativistic magnetic monopole flux constraints from RICE

We report an upper limit on the flux of relativistic monopoles based on the nonobservation of in-ice showers by the Radio Ice Cherenkov Experiment (RICE) at the South Pole. We obtain a 95% C.L. limit of order 10{sup -18} (cm{sup 2} s sr){sup -1} for intermediate-mass monopoles of 10{sup 7}{<=}{gamma}{<=}10{sup 12} at the anticipated energy E{sub tot}=10{sup 16} GeV. This bound is over an order of magnitude stronger than all previously published experimental limits for this range of boost parameters {gamma} and exceeds 2 orders of magnitude improvement over most of the range. We review the physics of radio detection, describe a Monte Carlo simulation including continuous and stochastic energy losses, and compare to previous experimental limits.