Extension of Fermi National Accelerator Laboratory magnetic-monopole search to 400 GeV

Abstract

In a search for magnetic monopoles an aluminum target has been exposed to 5.7 \ifmmode\times\else\texttimes\fi{} ${10}^{16}$ protons of 400 GeV energy at the Fermi National Accelerator Laboratory. The search apparatus employs equipment used previously in a search for monopoles produced by 300-GeV protons where a cross section of 6 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}42}$ ${\mathrm{cm}}^{2}$ was established using an iron dump. For the 400-GeV experiment the equipment was modified to detect magnetic charges down to $\frac{1}{30}$ of the Dirac magnetic charge. No magnetic monopoles were found with magnetic charges in the interval from $\frac{1}{30}$ to 24 times the Dirac magnetic charge. The upper limit at a 95% confidence level for the cross section per nucleon in aluminum is 5.1 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}42}$ ${\mathrm{cm}}^{2}$.