A Search for Fractionally Charged Particles Using the CERN Proton Synchrotron.

A search has been made for particles of fractional electric charge, produced at small angles from an internal Be target in the CERN Proton Synchroton. No such particles were found, leading to the following upper limits for the production cross-sections (90% confidence level) at 27 GeV/c incident-proton momentum: $$\begin{gathered} electric charge - \tfrac{1}{3}e; d^2 \sigma /d\Omega dp< 7.2 \times 10^{ - 39} at \Theta = 0 mrad, \hfill \\ electric charge - \tfrac{2}{3}e; d^2 \sigma /d\Omega dp< 5.2 \times 10^{ - 38} at \Theta = 6.5 mrad, \hfill \\ electric charge - \tfrac{1}{3}e; d^2 \sigma /d\Omega dp< 2.6 \times 10^{ - 35} at \Theta = 44 mrad, \hfill \\ electric charge - \tfrac{2}{3}e; d^2 \sigma /d\Omega dp< 1.3 \times 10^{ - 35} at \Theta = 44 mra \hfill \\ d \hfill \\ \end{gathered} $$