We have conducted a search for extended energy deposition trails left by ultrarelativistic magnetic monopoles interacting in Antarctic ice. The nonobservation of any satisfactory candidates in the 31 days of accumulated ANITA-II (Antarctic Impulsive Transient Antenna) flight data results in an upper limit on the diffuse flux of relativistic monopoles. We obtain a 90% C.L. limit of order ${10}^{-19}({\mathrm{cm}}^2\mathrm{s}\mathrm{sr}{)}^{-1}$ for values of Lorentz factor, $\gamma$, ${10}^{10}\le \gamma$ at the anticipated energy $E_{\mathrm{tot}}={10}^{16}\mathrm{GeV}$. This bound is stronger than all previously published experimental limits for this kinematic range.

• Received 19 August 2010

DOI:https://doi.org/10.1103/PhysRevD.83.023513