Search for fractionally charged particles in Kamiokande II

A search has been made for fractionally charged particles with $|Q|=\frac{1}{3}$ and $|Q|=\frac{2}{3}$ which might have passed through the Kamiokande II detector. No positive evidence for such particles is observed in 1009 days of observation. The 90%-C.L. upper limits obtained on the fluxes of fractionally charged particles are 2.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}15}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ ${\mathrm{s}}^{\ensuremath{-}1}$ ${\mathrm{sr}}^{\ensuremath{-}1}$ for $|Q|=\frac{1}{3} \mathrm{and} 2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ ${\mathrm{s}}^{\ensuremath{-}1}$ ${\mathrm{sr}}^{\ensuremath{-}1}$ for $|Q|=\frac{2}{3}$, improving the existing limits by two orders of magnitude.