Search for Grand-Unified-Theory Magnetic Monopoles at a Flux Level below the Parker Limit

Abstract

We report the results of the first direct search for grand-unified-theory magnetic monopoles with adequate sensitivity to detect a flux as small as the Parker flux limit. If stable monopole-nucleus bound states exist then the observed absence of monopole tracks in our 4.6\ifmmode\times\else\texttimes\fi{}${10}^{8}$-yr-old mica detector places an upper limit of ${10}^{\ensuremath{-}17}$ to ${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ ${\mathrm{sr}}^{\ensuremath{-}1}$ ${\mathrm{s}}^{\ensuremath{-}1}$ on the flux of grand-unified-theory monopoles having velocity $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}c$ to $1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}c$.