Ultrarelativistic magnetic monopole search with the ANITA-II balloon-borne radio interferometer

Abstract

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 ${10}^{\ensuremath{-}19}\text{ }\text{ }({\mathrm{cm}}^{2}\text{ }\mathrm{s}\text{ }\text{ }\mathrm{sr}{)}^{\ensuremath{-}1}$ for values of Lorentz factor, $\ensuremath{\gamma}$, ${10}^{10}\ensuremath{\le}\ensuremath{\gamma}$ at the anticipated energy ${E}_{\mathrm{tot}}={10}^{16}\text{ }\text{ }\mathrm{GeV}$. This bound is stronger than all previously published experimental limits for this kinematic range.